During my numerous excursions in these islands, I had in the majority of instances to follow up the stream-courses in order to examine their geological structure. I had therefore good opportunities in these regions of making a collection of the fresh-water shells, which, together with the land shells I collected, formed a total of between sixty and seventy species, amongst which there were 11 new species and at least 5 new varieties, whilst about 14 would appear to have been never previously recorded from the Solomon Islands, and there were in addition several from new localities in the group. The collection was sent to the British Museum and was examined and described by Mr. E. Smith, to whose paper on the subject[479] I am indebted for my acquaintance with the shells in question, and through whose kindness I have been thus enabled to supplement my other observations in these islands. A list of the shells with the descriptions of the new species is given on page 344. For its size, my collection presented a large amount of novelty, coming as it did from a region the land and fresh-water shells of which were previously considered to be fairly known. There can be no doubt, however, that in the Solomon Islands the conchologist has much work that remains to be done. Not only are the higher regions of the larger islands, entirely unexplored, but it would appear from the collections made up to the present date in this large group, that particular species may be not only confined to a special sub-group of islands but may be restricted to a single island, and that other species more widely distributed through the group may be represented in each island and in different districts of the larger islands by different varieties. Had I been aware of the extent of the influence of locality in this region, I might have made my collection of greater value. It would therefore seem necessary for future collectors in this group to make in every small island and in different districts of the larger islands special independent collections, disregarding the fact that they may have apparently met with the same shell very frequently before, because many of the varieties and some of the species can only be distinguished by the practised eye of the specialist, and a new locality for a previously well-known species may be often unwittingly found.

As an instance of the unexpected results, which may fall to the lot of others in this group, I may here add, that out of eleven land and fresh-water shells that I collected in the small island of Santa Anna, which is only 2¹/₂ miles in length, four were new species, and besides there were some new varieties. The stations of these four species may be suggestive. Two of them—Helix (Videna) sanctÆ annÆ and Helix (nanina) solidiuscula—were generally found on the trunks of the cocoa-nut palms at the coast; whilst the other two occurred in situations far more likely to yield new species, Melania sanctÆ annÆ being obtained from a small stream in the interior of the island, and Melania guppyi being found dead in the stomach and intestines of a fish that frequents the fresh-water lake of Wailava. This last shell would appear to live in the deeper parts of the lake, as I only found one living specimen, all the others being obtained from the stomach and intestines of these fish. Mr. Smith describes it as “a very remarkable and distinct species.” Its length is about 1¹/₅ inches; and its sharp-pointed spire was to be sometimes seen protruding through the vent of the fish, which evidently digests the animal and ejects the shell. These fish were usually 9 or 10 inches long; but the full-grown shells were found also in fish half this size, when the relation between the length of the shell and the size of the fish was truly alarming. Since the little fish actually swallow sharp pointed shells measuring a fifth of their own length and pass them out through the vent after they have digested the animal, we must credit them with a remarkable capacity for adapting their diet to circumstances.

To exemplify the variation which some species of shells display in this group, I will take the instance of Helix (Geotrochus) cleryi, RÉcluz. This species is probably distributed through the whole group; but considerable variation prevails in different islands. Amongst the several forms which I obtained, three were named as new varieties, var. meridionalis from Santa Anna, var. simboana from Simbo or Eddystone Island, and var. septentrionalis from the islands of Bougainville Straits, the localities of the two last varieties being only 80 miles apart. Mr. Smith remarks that this species is “subject to considerable variation in size, colour, and form, apparently resulting from difference of habitat. ........ Whether these several varieties should take specific rank is questionable, for, although there is a considerable difference between the extreme forms, even in the series of nearly one hundred specimens under examination, the gradual transition from one form to another is observable.”

Amongst the more singular in appearance of the land shells, I may refer to the large Bulimus (B. cleryi) which I found on the north coast of St. Christoval. It attains a length of four inches. I was never able to get a living specimen, as they are said by the natives to live in the foliage of the high trees. The specimens which I obtained were empty shells which the natives of the Koofeh district on the north coast of St. Christoval are in the habit of throwing into heaps, each man when he picks up a shell throwing it into the next heap he passes. I was unable to learn the reason of this practice and the natives did not seem willing to tell me. ... Two other Bulimi I commonly met with. One was the pretty Bulimus miltocheilus (Reeve), which, when the animal is young and the shell delicate, has a greenish-yellow hue resembling the colour of the leaves it feeds upon: as it grows older the shell becomes thicker and stronger, and in proportion as there is less need for protective resemblance, the greenish-yellow hue fades away, leaving a dull white colour behind. This species is found in St. Christoval and the adjacent islands. The other Bulimus (B. founaki, Homb. Jacq.) which I found in Faro Island, Bougainville Straits, and which had been only previously obtained at Isabel Island, attains a length of rather under three inches.

I come now to refer to the fresh-water shells of these regions. Stated in their order of frequency, the NeritinÆ, MelaniÆ, and NavicellÆ are the common fresh-water shells of these islands. The NeritinÆ were especially interesting to me. They abound in the streams: some of them preferring the moist rocks above the water, others finding their home in the waters of a quiet pool, whilst others, like the NavicellÆ, prefer to buffet the full rush of the torrent. An important feature with reference to these fresh-water Nerites or NeritinÆ is their wide dispersal. “Some of these species”—as Mr. Smith remarks in respect of those in my collection—“range not only through most of the islands of the Solomon Group, but have a considerably wider distribution.” Thus, Neritina subsulcata (Sowerby) and N. cornea (LinnÉ), are not only found in the Solomon Islands, but also occur in the Philippines: N. macgillivrayi (Reeve) and N. petiti (RÉcluz) alike exist in the Fiji and in the Solomon Groups; while N. porcata (Gould) has been found in Samoa and in Fiji as well as in the opposite extremities of the group with which I am at present concerned. Being interested in the question of the mode of dispersal of these Nerites, I made the following experiment to test their powers of sustaining submersion in salt-water. One individual belonging to the species Neritina subsulcata[480]—a species which is also found as above stated in the Philippines, and at the same time is the most widely dispersed fresh-water Nerite in the Solomon Group—survived a submersion of twelve hours; but not one out of a dozen individuals was found alive after a submersion of five days, although the water was changed from time to time. The result was a surprise to me, as I inferred from the result of Baron Aucapitaine’s experiments as related by Mr. Darwin,[481] that their close-fitting stony opercula would have enabled them to resist the action of salt-water. Their death could have been scarcely due to want of food, since I have kept shells of this species for several months on a very scanty diet, and since the powers of endurance of other fresh-water shells are well known. The matter passed out of my mind until after my arrival in England, when Mr. Smith put the question to me, as to their mode of dispersal. I then remembered that their calcareous egg-capsules, which are so commonly seen on the rocky sides of the streams, are in all probability sufficiently thick to resist the action of salt-water. Here is therefore a probable mode of dispersal, and I see it is one which Mr. Smith refers to as such in his paper. These egg-capsules “if attached to floating timber, might be carried to considerable distances.” They are often to be observed on the outside of the shells of living NavicellÆ, and I have seen them on the backs of the valves of a Unio which I discovered in the Shortland Islands.

One common feature of these fresh-water shells, whether NeritinÆ, NavicellÆ, or MelaniÆ, is the extensive erosion of the apices and surrounding parts of the shells. In some instances I have noticed that almost the entire exterior of the shell has been extensively eroded, particularly in the case of Neritina subsulcata, but I always found that the erosion was greatest in non-calcareous districts, where the free carbonic acid in the water is not all consumed in the solution of the limestone rocks. In volcanic islands the erosion of the fresh-water shells is greater than in islands of calcareous formation; and in streams, which, like those of the north coast of St. Christoval, flow in the upper portion of their course through a district of volcanic rocks and in the lower portion through a district of calcareous rocks, the same difference in the degree of erosion may be observed. I learn from a recent work by Professor Semper[482] that it is the boring of a minute fungus which first exposes the calcareous substance to the action of the carbonic acid, and that the mechanical action of the stream in forming tiny whirl-pools in the cavity probably assists in the erosion.

There are two common species of Neritina in these islands which I often confounded, viz., N. subsulcata and N. cornea; and I learn from Mr. Smith’s paper that these two species very closely approach each other. They, however, are usually to be found in different stations, N. cornea occurring on the trunks of palms and other trees away from the streams,[483] and N. subsulcata preferring the moist rocky sides of the streams a foot or so above the water.[484] Now and then they may be found encroaching on each other’s domain; for I have found them together on the trunks and branches of areca palms and tree-ferns in low lying moist districts, whilst, as at Choiseul Bay, I found them together in the streams.[485] Now it is a significant circumstance, that the specimen of N. cornea in my collection which was found by Mr. Smith to make the nearest approach to N. subsulcata was one which I obtained from a stream in Choiseul Bay. It had, in this case, not only intruded on the station of N. subsulcata, but had also assumed some of the distinctive characters of that species. It, therefore, seems to me probable that a graduated series of the shells of these two species might be formed, which would present the stages of transition from the one species to the other. If this be possible, then I would suggest that the fresh-water Nerite (Neritina subsulcata) may have been transformed into the tree Nerite (Neritina cornea) in the following manner.

I have already referred to the circumstance that in the higher portions of the St. Christoval streams, where the rocks are entirely volcanic, the fresh-water shells—and I may here add, especially those of Neritina subsulcata—suffer much more erosion than do shells of the same species in the lower parts of the streams where they flow through calcareous districts. Now, the geological structure of this island being mainly ancient volcanic rocks incrusted near the coast by recent calcareous formations, the time will come when these calcareous envelopes will have been entirely stripped off by denudation. How this will influence the Nerites of the streams may be thus explained. At present the normal characters of the species are preserved in the calcareous portions of the streams; but when all the calcareous rocks have been stripped off by denudation, the Nerite through its whole lifetime will be subjected to that extensive process of erosion, which now often denudes almost the entire surface of the shells of those individuals that live in the volcanic portion of the stream’s course. Here, Natural Selection may step in to favour the survival of any slight variation that makes the Nerite more suited to lead an entirely arboreal existence. Such a geological agency may in truth lead finally to the expulsion of the Nerite from the stream’s course. Varieties will survive only in proportion to their capability of adapting themselves to the new condition; and they alone will perpetuate their kind until a tree Nerite of distinct specific character is produced. ... On this reasoning, tree Nerites ought to be more numerous in islands of volcanic formation; but this is a point on which I cannot pronounce from the lack of sufficient evidence.[486]

According to Professor Semper, we have in Navicella “a modified form of Neritina,” which genus it resembles in all essential anatomical characters, but “by long inurement to living in rushing mountain streams, it has had its shell modified in the way most suited to those conditions, while the operculum, in consequence of long disuse, has become a peculiar degenerate or rudimentary organ.”[487]

The growth of the fresh-water Nerites would appear to be slow. I kept a young individual of Neritina subsulcata for seven months in a bottle partly filled with rain-water, and supplied it with decaying leaves for food which it used to eat. Its weight was 37 grains both at the beginning and the end of the experiment, having only varied half a grain during the whole time; and its dimensions, as determined by measurement, were unaltered. This species, when it is first picked off the rock, ejects a watery fluid with a powerful musky odour, which effect accompanies the closure of the shell by the operculum. I kept some individuals of this species in rain-water, containing varying proportions of lime-water, for about three months. The lime-water was of the medicinal strength of the British Pharmacopeia. I began with water containing 64 parts of rain-water to one part of the lime-solution. By the end of the first month the proportion was increased to 32 to 1; by the end of the second month it was 16 to 1; towards the end of the third month the Nerites, having lived for over three weeks in the last solution, began to die; the survivors were placed in a solution containing the proportion of 8 to 1, but this amount of the lime-solution proved too much for them. It should be remarked that throughout the experiment, the Nerites used to descend to the water to get their food just as frequently as in the state of nature: they did not avoid the water; and after the experiment was over, there was no apparent alteration in the appearance of the shells. These observations were made in the north part of New Zealand during the latter part of the summer and the beginning of the autumn, a circumstance which may partially explain the death of the shells. The temperature there was about 20° below the temperature they are accustomed to in the Solomon Islands; this difference is of interest when it is remembered that NeritinÆ are mostly found in the streams of tropical regions; and I may, therefore, infer that this species is capable of adapting itself to temperatures much lower than that to which it is accustomed, since some individuals survived the voyage to New Zealand from the Solomon Islands and lived in the climate of the former region for three months under very unfavourable conditions.

Professor Semper[488] remarks that some NeritinÆ have the habit of detaching themselves from rocks on the slightest touch, by this means, as he considers, escaping the pursuit of their enemies. Some of them, however, as I observed, detach themselves spontaneously and independently of any alarm. The individuals of Neritina subsulcata that I kept in a large bottle in my cabin, used frequently in the course of a night to detach themselves from the sides and drop down into the water below. On one occasion when the noise woke me up, I found the culprit voraciously eating a portion of decayed leaf. In the daytime they sometimes dropped, and at other times crawled, down to the water. ..... It is probable that the musky water, which this Nerite ejects when it is picked off a rock, may cause a bird to drop it from its beak and thus save its life.

Amongst the new fresh-water shells that I found in this group was a species of Unio, to which Mr. Smith did me the honour of attaching my name, it being the first species of this genus of river-mussels that has been found in the Solomon Group. But its occurrence there means something more than a new locality, since, as I believe, I am correct in asserting, we have in it the first record of this widely distributed genus having reached the Pacific islands. I do not think that this species can be generally spread through the Solomon Group. I only found it in one locality, namely the Shortland Islands, near the western end of the group.

A very familiar shell, in low-lying moist and marshy situations throughout the Solomon Islands, is that of the auriculoid, Pythia scarabÆus, LinnÉ. Being usually accustomed to find it in the low-lying districts, I was surprised on one occasion to find it in the higher parts of Faro Island, which attains an elevation of 1,900 feet above sea. In the mangrove swamps and in the lower parts of the streams at Choiseul Bay, I found a species of Cyrena which has not yet been described, together with Cerithidea cornea (A. Adams: var.) and Pyrazus palustris, the last species occurring also in India. On the moist ground of the taro patches in the islands of Bougainville Straits thrives a species (S. simplex, var.) of that ubiquitous genus Succinea. The operculated land-snails, of which the HelicinÆ are the most numerous, are found more frequently in calcareous districts.

LIST OF LAND AND FRESH-WATER SHELLS COLLECTED IN THE SOLOMON ISLANDS[489] DURING 1882 AND 1883. (EXTRACTED FROM MR. E. SMITH’S PAPER IN THE PROCEEDINGS OF THE ZOOLOGICAL SOCIETY OF LONDON, JUNE, 2ND, 1885.) THE DESCRIPTIONS OF THE NEW SPECIES AND VARIETIES FOLLOW:

(1) Helicarion planospira (Pfeiffer) Hab. Santa Anna, Ugi, St. Christoval, Guadalcanar.

(2) Helix (Nanina) nitidissima (nov. spec.) Hab. Treasury Island, a variety in Guadalcanar.

(3) Helix (Nanina) solidiuscula (nov. spec.) Hab. Santa Anna, found generally on the trunks of cocoa-nut palms.

(4) Helix (Corasia) tricolor (Pfeiffer) Hab. St. Christoval, Ugi, Santa Anna.

(5) Helix (Corasia) anadyomene, A (Adams & Angas) Hab. Guadalcanar, Ugi.

(6) Helix (Geotrochus) acmella (Pfeiffer) Hab. Faro Island, Bougainville Straits; Florida Islands, vide original paper.

(7) Helix (Geotrochus) gamelia (Angas) Hab. Isabel, Stephen Island, Shortland Islands, Treasury Island, Choiseul Bay.

(8) Helix (Geotrochus) hargreavesi (Angas) Hab. Faro Island in Bougainville Straits.

(9) Helix (Geotrochus) mendana (Angas) Hab. Shortland Islands, vide original paper.

(10) Helix (Geotrochus) motacilla (Pfeiffer) Hab. Simbo or Eddystone Island, also called Narovo.

Note.—In the original paper, Simbo and Eddystone are referred to as two different islands. This mistake arose from the omission of the name of Simbo in the latest charts; it is, however, the name usually employed.

(11) Helix (Geotrochus) guppyi (nov. spec.) Hab. Faro Island in Bougainville Straits.

(12) Helix (Geotrochus) dampieri (Angas) var. Hab. Choiseul Bay.

(13) Helix (Geotrochus) eros (Angas) Hab. Isabel, Stephen Island, Shortland Islands.

(14) Helix (Geotrochus) cleryi (RÉcluz) Hab. Santa Anna, Ugi, St. Christoval, Guadalcanar, Rua Sura Islets, New Georgia, Simbo or Eddystone, Treasury, Shortlands, Choiseul Bay. Three new varieties, var meridionalis (Santa Anna), var simboana (Simbo or Eddystone), var septentrionalis (Shortlands, Treasury, Choiseul Bay.)

(15) Helix (Videna) merziana (Pfeiffer) Hab. St. Christoval, New Georgia, Ugi; vide original paper.

(16) Helix (Videna) sanctÆ annÆ (nov. spec.) Hab. Santa Anna, living on the trunks of cocoa-nut palms.

Note.—This species, or a closely similar form, was observed by me in many other islands; but I neglected to collect it in any other locality than Santa Anna.

(17) Helix (Rhytida) villandrei (Gassies) Hab. St. Christoval, Ugi.

(18) Helix (CamÆna) hombroni (Pfeiffer) Hab. Shortland and Faro Islands in Bougainville Straits, Isabel.

(19) Helix (Chloritis) eustoma (Pfeiffer) Hab. New Georgia, Ugi, Faro Island (Bougainville Straits.)

(20) Bulimus (Placostylus) cleryi (Petit) Hab. St. Christoval.

(21) Bulimus (Placostylus) founaki (Hombron and Jacquinot) Hab. Isabel, Faro Island (Bougainville Straits).

(22) Bulimus (Placostylus) miltocheilus (Reeve) Hab. St. Christoval (S.E. part), Ugi, Santa Anna: vide original paper.

(23) Partula, spec. Hab. Guadalcanar, Ugi, Treasury Island, Choiseul Bay: vide original paper.

(24) Succinea simplex (Pfeiffer) var. Hab. Treasury Island, Shortland Islands: living on the moist ground in the taro patches.

(25) Cyclostoma (Adelostoma) triste (Tapparone Canefri), var? Hab. Guadalcanar; Santa Anna; Faro and Shortland Islands and Choiseul Bay in Bougainville Straits.

(26) Leptopoma jacquinoti (Pfeiffer) Hab. Rua Sura Islets off the north coast of Guadalcanar: vide original paper.

(27) Leptopoma vitreum (Lesson) Hab. Santa Anna, Simbo or Eddystone; Shortland Islands.

(28) Omphalotropis nebulosa (Pease) Hab. St. Christoval, Guadalcanar, Ugi. I found this shell living on trees clothing a low tract of land skirting the beach.

(29) Pupina solomonensis (nov. spec.) Hab. Shortland and Treasury Islands in Bougainville Straits: living in the decayed trunks of fallen trees.

(30) Hargravesia polita, H. (Adams), var. Hab. Faro Island in Bougainville Straits: vide original paper.

(31) Helicina moquiniana (RÉcluz) Hab. St. Christoval, Guadalcanar, Ugi.

(32) Helicina egregia (Pfeiffer) Hab. Guadalcanar, Florida Islands.

(33) Helicina modesta (Pfeiffer) Hab. Guadalcanar, Shortland Islands, Treasury Islands, Choiseul Bay.

(34) Helicina solomonensis (nov. spec.) Hab. The Islands of Bougainville Straits (Faro, Shortlands, Treasury).

(35) Pythia scarabÆus (LinnÉ) Hab. Santa Anna, St. Christoval, which were the localities of my specimens; but I observed this species and its varieties in every island I visited. Stat: Moist ground usually near the sea.

(36) Melampus fasciatus (Deshayes) Hab. Isabel, Rua Sura Islets off the north coast of Guadalcanar. I found these shells in the crevices of a log on the beach.

(37) Melania amarula (LinnÉ) Hab. Ugi, in the streams.

(38) Melania scabra (MÜller) Hab. Ugi, in a stream.

(39) Melania salomonis (Brot.) Hab. Ugi, in a stream.

(40) Melania fulgurans (Hinds) Hab. Ugi, in a stream.

(41) Melania fastigiella (Reeve) Hab. Imbedded in a dark calcareous loam exposed in the banks of a large stream near its mouth at Sulagina, on the north coast of St. Christoval. I could not find any living specimens.

(42) Melania spec. Hab. The same as Mel. fastigiella.

(43) Melania verrucosa (Hinds) Hab. The same as Mel. fastigiella.

(44) Melania subgradata (nov. spec.) Hab. The same as Mel. fastigiella.

(45) Melania ugiensis (nov. spec.) Hab. From a stream in Ugi.

(46) Melania sanctÆ annÆ (nov. spec.) Hab. A stream in the interior of Santa Anna.

(47) Melania guppyi (nov. spec.) Hab. From the stomach and intestines of a fish living in the fresh-water lake of Wailava in the island of Santa Anna. This species probably frequents the deeper parts of the lake, as I only found one living individual.

(48) Cerithidea cornea A. (Adams) var. Hab. Mangrove swamps in Choiseul Bay.

(49) Pyrazus palustris Hab. Mangrove swamps in Choiseul Bay.

Note.—Not referred to in original paper.

(50) Nerita marmorata (Hombron and Jacquinot) Hab. Living just above high-water level on the surface of the coral-limestone coast, St. Christoval.

(51) Neritina cornea (LinnÉ) Hab. Star Harbour, St. Christoval, on the trunks of trees 150 feet above the nearest stream; Choiseul Bay, from a stream; Shortland Islands, on the stems of tree-ferns and areca palms in a marshy district. I found this species in many other islands; but did not collect it except in the above three localities.

(52) Neritina subsulcata (Sowerby) Hab. Streams in St. Christoval and in the islands of Bougainville Straits. In the Shortland Islands I found this species on the stems of tree-ferns and areca palms in a marshy district. I only collected it in these localities; but I found it in many other islands. When first picked off the rock, it ejects a watery fluid possessing a powerful musky odour.

(53) Neritina dubia (Chemnitz) Hab. Shortland Islands, in a stream.

(54) Neritina adumbrata (Reeve) Hab. A stream in Choiseul Bay, and the rocky sides of a stream-course in Ugi.

(55) Neritina pulligera (LinnÉ) Hab. Guadalcanar, St. Christoval, Ugi, Choiseul Bay, in the streams.

(56) Neritina petiti (RÉcluz) Hab. Treasury and Faro Islands, in the streams.

(57) Neritina olivacea (Le Guillou) Hab. Streams in Treasury Island and at Sulagina, St. Christoval.

(58) Neritina macgillivrayi (Reeve) Hab. Streams in Guadalcanar and in Faro Island, Bougainville Straits.

(59) Neritina asperulata (RÉcluz) Hab. Rocky sides of a stream-course in Ugi.

(60) Neritina porcata (Gould) Hab. St. Christoval, and Faro Island, Bougainville Straits, in streams.

(61) Neritina variegata (Lesson) Hab. St. Christoval, Ugi; Simbo or Eddystone; Faro Island, Bougainville Straits; Choiseul Bay; in streams.

(62) Neritina turtoni (RÉcluz) Hab. A stream in the Shortland Islands; streams in Guadalcanar; imbedded in a dark calcareous loam exposed in the banks of a large stream near to its mouth at Sulagina on the north coast of St. Christoval.

(63) Neritina brevispina (Lamarck) Hab. Streams in Shortland, Treasury, and Ugi Islands. The specimens from Treasury Island were destitute of spines.

(64) Neritina squarrosa (RÉcluz) Hab. Streams in Treasury Island.

(65) Navicella sanguisuga (Reeve) Hab. Streams in Faro Island, Bougainville Straits.

(66) Navicella suborbicularis (Sowerby) Hab. Guadalcanar, St. Christoval, Ugi, Treasury and Faro Islands in Bougainville Straits.

(67) Unio guppyi (nov. spec.) Hab. Streams in the Shortland Islands.

(68) Cyrena, spec. Hab. In the lower parts of streams and in mangrove swamps, Choiseul Bay. Note.—This species is not referred to in the original paper.

Descriptions of the new species and varieties,[490] by Mr. E. Smith.

(2) Helix (Nanina) nitidissima. (Plate XXXVI. figs. 1, 1 b.) Shell thin, transparent, very glossy, depressed, narrowly perforate, pale brownish horn-colour above, whitish towards the umbilicus, sculptured with very faint lines of growth. Whorls 4-5, slightly convex, impressed and marginate above at the suture; last whorl large, rounded at the periphery. Aperture obliquely lunate; peristome simple, thin, slightly thickened and reflexed partly over the perforation. Spire low, but very little raised above the last whorl, obtuse at the apex. Greatest diameter 14 millim., smallest 12; height 9.

(3) Helix (Nanina) solidiuscula. (Plate XXXVI., figs. 2, 2 b.) Shell very narrowly perforate, depressed, somewhat solid, dark chestnut-brown and a little glossy above, more shining and paler beneath, becoming almost white at the umbilical region; whorls 6¹/₂, convex, separated by a deepish suture, and, with the exception of two or three at the apex which are smooth, sculptured with strong, close-set, arcuate, and oblique striÆ on the upper surface, crossed with a few more or less distinct spiral lines. Body-whorl rounded at the periphery, or sometimes with the faintest indication of an angle, convex, and only exhibiting fine lines of growth below. Aperture obliquely semi-lunate; peristome simple, but, owing to the solidity of the shell, seeming slightly thickened, especially on the very oblique columellar margin, which is shortly reflexed above over the perforation. Spire depressed-conoid, having the least convex outlines and an obtuse apex. Greatest diameter 18 millim., smallest 16¹/₂, height 12; aperture 8 long, 4¹/₂ wide.

This species is well distinguished by its comparative solidity and strong sculpture on the upper surface.

(4) Helix (Corasia) tricolor (Pfeiffer). (Plate XXXVI., figs. 3, 3 b.) A specimen obtained on the north coast of the same island of St. Christoval, by Mr. Guppy, is worthy of special mention, and may be termed var. picta, on account of the undulating reddish-brown stripes which ornament both the upper and lower surfaces.

A similar example was also collected by Dr. A. Corrie and presented to the Museum. The markings on these two shells are very striking and distinctly visible within the aperture.

(11) Helix (Geotrochus) guppyi. (Plate XXXVI. fig. 4.) Shell elevately conical, thin, pale yellow, ornamented with conspicuous nearly black or black-brown spiral bands, one above and one below the sutures of the upper whorls, and three upon the last, one sutural, the second peripheral, and the third basal. Volutions 6, rather slowly enlarging, a little convex, sculptured with fine oblique striÆ of growth, not glossy. Three first whorls livid purplish, the last rather sharply angled at the middle, not descending in front, having the basal band broad around the almost concealed perforation, and obsolete within the aperture. The latter is oblique, somewhat narrowed and pouting in front, banded within with three almost black and two white bands, the central one of the former being squarely truncate at the end, only the lower corner of it touching the margin of the lip, which is pale oblique, receding, a little expanded and reflexed in front and at the columellar margin, the upper end of which is spread over and nearly conceals the small umbilicus. Height 22¹/₂ millim., greatest diameter 19, smallest 16.

This species is remarkable for the striking contrast of its colour-bands and the angular character of the last whorl.

(12) Helix (Geotrochus) dampieri, Angas, var. (Plate XXXVI. fig. 5.) Shell imperforate, subglobose, conoid, light brown or fawn-colour, here and there minutely dotted with dark-grey specks, with a broad white band around the middle of the penultimate whorl and two upon the last, one above and the other below the middle, also a narrow white line revolving up the spire beneath the suture, and a dark brown zone surrounding the pale or yellowish umbilical region. Whorls 5, a little convex above, somewhat glossy, obliquely and very finely striated by the lines of growth, the last more or less concentrically striated beneath, shortly descending at the aperture which is white within. Lip a little thickened, edged with reddish brown, only slightly expanded on the right side, more dilated below, produced into a thin transparent callosity over the umbilical region, united above to the upper extremity of the peristome. Columellar margin oblique, white or partly tinged with reddish brown, thickened and terminating below within the edge of the lip. Height 19 millim., greatest diam. 22, smallest 19.

The specimens from the Solomon Islands are smaller than the type with which, through the kindness of Mr G. F. Angas, I have compared them. They also have the peristome brown, and the basal band is darker.

(14) Helix (Geotrochus) cleryi, RÉcluz (Plate XXXVI. figs 6, 6 b). The specimens from Santa Anna (var. meridionalis fig. 6 b) are smaller than the type, pale brown above, with a white thread-like line at the suture, and the acutely keeled periphery, paler beneath, especially towards the centre, and have the aperture particularly acuminate at the termination of the keel.

The specimens from Simbo (var. simboana, fig. 6 a) are uniformly pale horn-colour, rather sharply carinate at the middle, and have the peristome white, considerably thickened and almost notched at the upper end of the columella, and the body-whorl is more contracted than in the typical form. The examples from Choiseul Bay, Shortland and Treasury Islands (var. septentrionalis, fig. 6) are all alike, of smaller dimensions than the normal form, thin pale brownish horn-colour, with rather more convex whorls than usual, the carina at the periphery being acute and thread-like as in the variety simboana.

Whether these several varieties should take specific rank is questionable, for, although there is considerable difference between the extreme forms even in the series of nearly one hundred specimens under examination, the gradual transition from one form to another is observable.

(16) Helix (Videna) sanctÆ annÆ. (Plate XXXVI. figs. 7. 7 b.) Shell depressed-conoid, deeply umbilicated, very acutely keeled at the periphery, light brown, sometimes with a few radiating pale streaks on the upper surface, sculptured with oblique lines of growth. Whorls 5, rather slowly increasing, slightly convex, depressed and margined above the suture, last not descending, compressed above and below the keel, a little convex towards the umbilicus, which is moderately large. Aperture transverse, flesh-tinted within. Peristome simple, a little thickened along the basal margin, with the extremities united by a thin callus. Height 7 millim.; greatest diameter 17, smallest 15.

(25) Cyclostoma (Adelostoma) triste, Tapparone Canefri, var.? Dr. Tapparone Canefri has kindly compared specimens from these islands with his C triste, and is of opinion that they may be considered a variety of it; and observes that the New-Guinean form is a little smaller, its spire a little more slender, its surface more glossy, the colour redder, and the apex of the spire darker.

The shells under examination are clothed with a very thin epidermis when in a fresh condition, exhibiting numerous very fine spiral thread-like lines, which entirely disappear in worn shells and can easily be rubbed off with a brush. For several species having a similar epidermis and an incomplete peristome, Dr. Tapparone Canefri has proposed the subgenus Adelostoma.

(29) Pupina solomonensis.(Plate XXXVI. fig. 9, 9 a.) Shell small and very like P. difficilis, Semper, and P. keraudreni, Vignard. It is of a reddish tint, especially the body-whorl; consists of 5¹/₂ whorls, which are the least convex and exhibit a pellucid line, frequently brown, immediately beneath the suture. Last whorl very obliquely descending behind, narrowed below, and flattened somewhat above the aperture. Columella thickened with callus, white, parted off from the whorl above by an oblique circumscribing red line, truncated rather low down. Outer lip slightly thickened and effuse, and a little paler than the rest of the whorl, produced somewhat at its junction with the body-whorl, which in consequence has the appearance of rising suddenly after an oblique descent. Length 7 millims., diam. 3²/₃, aperture 2 long and wide.

(34) Helicina solomonensis. (Plate XXXVI. figs. 11, ll b.) Shell small, globose-conical, reddish or yellowish, pale at the apex. Whorls 4-4¹/₂, the least convex above, sculptured with lines of growth and fine spiral striÆ both on the upper and lower surfaces, very faintly margined above at the suture; last whorl rounded at the periphery, obsoletely angled near the junction of the outer lip and the least descending in front, so that the faint angulation is visible for a short distance above the sutural line. Aperture somewhat semicircular and oblique, small; peristome slightly expanded; umbilical callosity yellowish or pellucid whitish, defined towards the base of the columellar margin. Greatest width 4²/₃ millim., smallest 4; height 3¹/₂.

(44) Melania subgradata.(Plate XXXVII. fig. 3, 3 a). Shell elongate, turreted, rather solid, covered with an (olive?) epidermis, and marked with fine longitudinal oblique red lines which extend from suture to suture. Whorls probably about 10, flat or even a little concave at the sides, shouldered above, usually with a spiral shallow groove and a few striÆ near the shoulder, and marked with fine incremental striÆ. Suture deep, slightly oblique. Last whorl long, finely transversely striated, most distinctly at the base. Aperture elongate-pyriform, acute above, effuse at the base. Outer lip thin, sharp, accurate, and prominent at the middle. Columellar margin rather thickly covered with callus, united above to the outer lip. Length of two specimens, consisting of five whorls 30 and 25 millim.; diameter 11 and 10¹/₂; aperture 14 and 12 long, 6 and 5 wide.

(45) Melania ugiensis. (Plate XXXVII. fig. 4.) Shell subulate, acuminate, beneath the epidermis (which is wanting in the specimens at hand), of a dirty, pale, livid, or purplish tint. Whorls probably about 14 in number; the eleven remaining are a little convex, rather slowly enlarging, and sculptured with close-set, obliquish, fine riblets, which are crossed by crowded spiral striÆ. Last whorl large, with the riblets rather obsolete below the middle, and very close together, much more numerous than those upon the upper whorls. Aperture obliquely pear-shaped. Length 25 millim., diameter 8; aperture 8¹/₂ long, 4¹/₂ wide.

(46) Melania sanctÆ annÆ. (Plate XXXVII. figs. 5, 5 a.) Shell small, acuminately pyramidal, somewhat eroded towards the apex, covered with a yellowish-olive epidermis, and sometimes marked with a few indistinct, reddish, irregular spots, and lines near the middle of the body-whorl. Whorls 5-6 remaining, flattish at the sides, divided by a slightly, oblique, distinct suture, all with the exception of the last one or two more or less distinctly, longitudinally, finely plicate; the plicÆ are more conspicuous in some specimens than in others, being at times entirely eroded. The other sculpture consists of fine lines of growth, and a few rather distant spiral striÆ, which cut across the incremental lines and produce a puckered appearance. Aperture elongate, pyriform, pale bluish within. Length of specimen consisting of six whorls 13 millim., diameter 5; aperture 5 long and 2¹/₂ wide.

(47) Melania guppyi. (Plate XXXVII. figs. 6, 6 a.) Shell slenderly acuminate, covered with an olive-brown epidermis. Whorls about 14, divided by a very oblique, deepish suture, concave above the middle and somewhat convex below it, and then contracted; ornamented with a few spiral series of nodules (about five on the upper whorls) and rather indistinct, very oblique and flexuous, longitudinal ridges, upon which the nodules rests, also exhibiting very sloping and flexuous lines of growth; the most conspicuous rows of granules are near the middle of the whorls. Aperture pyriform. Outer lip thin, remarkably sinuated above towards the suture, and arcuately prominent below. Columellar margin oblique, straightish, covered with a callus, curving into the broad basal sinus. Length 31 millim., diameter 7; aperture 9 long, 4 wide.

This is a very remarkable and distinct species, with a very drawn-out spire, peculiar granuled sculpture, and a deeply sinuated labrum. I have much pleasure in naming it after Mr. Guppy.

(66) Unio guppyi. (Plate XXXVII. figs. 8-8 b.) Shell elongate, very inequilateral, usually a little longer than twice the height, compressed, covered with a blackish-brown epidermis, exhibiting strong lines of growth, and very faint radiating substriation, and marked with fine wrinklings at the eroded beaks, which are small and placed quite near the anterior extremity. Dorsal margin behind the umbones almost straight or the least excurved for some distance, then at an obtuse angle becoming oblique before rounding into the extremity, which is a little more sharply curved than the anterior end. Ventral outline either faintly excurved, straight, or the least concave. Interior bluish-white, most iridescent at the hinder extremity, generally stained in parts with olive-brown. Cardinal tooth of the right valve moderately large, four or five-lobed at the top, situated just in front of umbo. Between it and the outer margin is a short ridge, the space between the tooth and the ridge receiving the single, smaller, roughened, and striated tooth of the left valve. Lateral tooth of the right valve long, obliquely truncate behind, fitting in between two teeth in the opposite valve. Anterior adductor scar deep, posterior superficial, squarish in front. Pedal scar in both valves under the cardinal tooth very deep. Ligament elongate, prominent.

This species recalls to mind some of the forms from Australia and New Zealand. Its principal features are the elongate compressed form, dark brown colour, wrinkled apices, and coarse incremental lines. It is the only species as yet recorded from the Solomon Islands.

ADDITIONAL NOTE. (H. B. GUPPY.)

A species of the LitoritinidÆ (Littorina scabra) is commonly found in this group on the leaves and trunks of mangroves, Barringtonias, and other littoral trees, the branches of which overspread the rising tide. These molluscs occur at heights varying from one or two feet to eight or nine feet above the high-water level; and they possess an unusually delicate operculum as compared with those of other species of the same family. They do not seem to be able to withstand immersion in salt water for any length of time, since out of six individuals kept submerged for twenty-four hours, three died. When first placed in the water, they were evidently very much out of their element, and tried in vain to creep out of the vessel. The delicate character of the operculum indicates a transitional stage between marine and terrestrial molluscs; and the experiment above referred to, throws a little light on this subject, since only the younger of the six individuals survived. One would have expected that the younger individuals would have been less able to withstand immersion in sea-water, but such was not the case, since they recovered from an immersion which killed the older individuals. In explanation of this unexpected result, I would infer that, on the theory of the inheritance of peculiarities at corresponding ages, the younger individuals would retain more of the marine habits of the original parent of the species, because in the first place only the adults of this parent species would have been modified to suit the new condition.