  DEFINITION OF THE ORDER SALIENTIA, LAURENTI, 1768. (World-wide distribution.) Naked, tailless Amphibia of compact form, and with usually procoelous vertebrÆ. Caudal vertebrÆ coalesced into a slender elongate piece, the urostyle. Two elements of the tarsus ossified and greatly elongated. Development by metamorphosis; gills never present in adult. Ilium greatly elongated. The order is suggested in the Coal Measures by a single species, known from a single poorly preserved specimen (plate 24, fig. 1). The form Pelion lyelli Wyman was the first known of the Linton Amphibia, and its striking frog-like (123, 639) appearance was early noticed. There is no assurance that the species belongs with this order, but since a well-developed and highly specialized frog (480, 481) occurs in the Como Beds (405) of Wyoming, it is not impossible that we may have in the Pelion lyelli a suggestion (460), at least, of the ancestral structure. It is certain that the frogs have, in past ages, had a much greater length of vertebral column than they possess at present, as is witnessed by the coalescence of several vertebrÆ to form the urostyle. It is suggested that the ancestral vertebral column is represented in Pelion. Family PELIONTIDÆ Cope, 1875. Cope, Bull. U. S. Nat. Mus., No. 1, p. II, 1875. The present family includes but a single species, that of Pelion lyelli Wyman, first described in 1858 (640), from Linton, Ohio. The family characters are to be found in the broad and obtusely rounded cranium, in the frog-like scapular arch, the frog-like hind limb, and in the form of the palate, so far as these structures have been preserved. It has been suggested that the present form shows decided affinities with the frogs of to-day and it may possibly be looked upon as the actual ancestor of the living frogs. The length of the vertebral column would seem to militate against such a relationship, since it is well known that frogs have had a short vertebral column since the Jurassic (480, 481). But this is not a good argument, since the developing urostyles of modern tadpoles show metameric fenestrations in the developing bone which doubtless correspond to openings between the vertebrÆ. The notochord of the tail is segmented, apparently through the influence of former vertebral structure. At any rate, the suggestion is an interesting one and, whether sustained or disproven, the present discussion is based on the probabilities of the case. Wyman, Am. Jour. Sci. (2), XXV, p. 160, 1858 (Raniceps). Cope, Proc. Acad. Nat. Sci. Phil., 1868, 211 (Pelion, suggested in letter to Cope by Wyman). Type: Pelion lyelli Wyman. "The only specimen of the species exhibits an inferior view of a portion of the skeleton; and the obverse, on which the thoracic and abdominal armor could have been preserved, has not come under my observation. The specimen, however, does not exhibit any ribs, although the vertebrÆ are well preserved. As observed by Professor Wyman, the genus presents some points of similarity to the Anura (Salientia). The prolongation of the angles of the mandible is of this character, as well as the general form of the head. The bones of the forearm may be united as in the frogs, and the length and curvature of the femur are seen among these animals rather than the Salamanders. The form of the femur is different from that of Amphibamus grandiceps Cope, which also differs in the presence of dermal scales and ventral scutellÆ." (123.) MOODIE Hylerpeton dawsoni Owen. Above: Mandible, teeth, rib, and bones of extremity. Below: Bones of pelvis and posterior limb and bony scales. Nearly natural size. Erect tree, Coal formation, South Joggins, Nova Scotia. Photograph by Dawson, published through the courtesy of Dr. Arthur Willey. Original specimens in Peter Redpath Museum of McGill University. Pelion lyelli Wyman. Wyman, Am. Jour. Sci. (2), XXV, p. 160, 1858. Cope, Proc. Acad. Nat. Sci. Phil., 1868, p. 211. Cope, Geol. Surv. Ohio, II, pt. II, p. 390, pl. XXVI, fig. 1, 1875. Moodie, Pop. Sci. Monthly, LXXII, p. 562, fig. 1, 1908. Type: Specimen No. 7909 G, American Museum of Natural History. Horizon and locality: Linton, Ohio, Coal Measures. (Plate 24, fig. 1.) This was the first species described from the Linton, Ohio, deposits. It was made known by Dr. Wyman in 1857 at the meeting of the American Association for the Advancement of Science for that year. The species was subsequently studied by Cope. He merely confirmed Wyman's observations. The following description is based on the descriptions of Cope and Wyman and on my own study of the type specimen. This is the most frog-like, in appearance at least, of all the Amphibia which have so far been discovered in the Carboniferous. The skull especially has a shape which is strikingly frog-like, and the long hind limbs lend further likeness to the tailless forms. Pelion may have been a jumping creature, if we may judge from its long hind legs. Wyman and Cope have both called attention to the frog-like appearance of the specimen, and this is apparent at the first glance. It is probable that the resemblance has some significance as to the ancestry of the Salientia, and it may indicate the first step in the origin of the tailless Amphibia. It is possible that the frogs began to be separated from the other Amphibia during the Carboniferous. The first frogs we know are from the Jurassic, where they are well-developed ranids. If Pelion be a frog ancestor, then the history of the group from the Coal Measures to Jurassic is an unknown story. The specimen is preserved on its back and it is thus impossible to tell as to the structure of the skull. Cope was of the opinion that the depressed areas on the sides of the elongate parasphenoid were the orbits, and if so the resemblance to the frogs is much more striking. In the frogs there is a strong process from the pterygoid which projects inward to meet a corresponding process from the parasphenoid. This forms a heavy rod behind the palatine vacuity. There is a heavy rod represented in the specimen and a part of it is certainly the external process of the parasphenoid, but whether it is to be interpreted as in the frog is an open question. The outline of the cranium is partially obscured by the mandibles, but the anterior part is represented by a raised line, as shown in figure 17. In the anterior part of this space there are two ridges which may be tooth ridges. If they are teeth there is a great similarity to the premaxillary and vomerine teeth of Necturus, since the ridges are widely separated at the median line and approximated distally, as they are in Necturus. The mandible is preserved entire and its form is strikingly frog-like. Its posterior angles project over the quadrate area and seem to have had an upturned projection such as is found in the mandibles of the Crocodilia. There are impressions of 20 vertebrÆ preserved, and they cover a little more than half of the presacral region. There may have been 28 to 30 presacrals. The Fig. 17. Pelion lyelli Wyman, an amphibian from the Coal Measures of Ohio, the supposed ancestral salientian. (After Wyman.) × 0.75. pmx, premaxilla; pv, palatine vacuity; m, mandible; sc, scapula-coracoid; h, humerus; r-u, radius and ulna; f, femur; t, tibia. There is an impression anterior to the right humerus which may represent a part of the pectoral girdle, but its form is so obscure that it can not be determined. The pelvic girdle is entirely wanting in the specimen. Remains of the fore and hind limbs are preserved. The arms are especially well preserved and consist of a strong humerus, a separate radius and ulna, and phalanges, the carpus having undoubtedly been cartilaginous, since there are no traces of carpal bones. Wyman has figured a small ossicle (fig. 17) which might be interpreted as a carpal, but it is further removed from the carpal region than his figure shows and I would interpret it as a fragment of a phalange, since the first digit seems to be turned aside over the vertebral column. The right hand is but imperfectly preserved, but the left hand is nearly entire. There are evidences of 4 digits, possibly 5. The metacarpals are elongate and rather stout. The phalanges of the distal series have been lost, so the phalangeal formula can not be determined. On the whole, the hand has a very broad aspect and is not at all slender, as in the majority of the microsaurians from the Coal Measures of Ohio. It resembles in a great measure the broad hand of a toad and may thus be indicative of a terrestrial life. The humerus is well developed and has pronounced swellings, as though for the attachment of strong muscles. These indications would favor the view of the animal being a land dweller. The femur and a part of the tibia (?) of the right side are all there is preserved of the hind limb. These elements show the leg to have been quite long, though weaker than the fore limb. The femur has a large distal articular surface. The fibula is, apparently, absent, though it may simply be lost. The genus Pelion stands alone among the Carboniferous Amphibia. The form can not be placed in the order Branchiosauria on account of the well-developed limb bones and the large mandible. It may belong with the Microsauria. I have placed it under the Salientia in the hope of learning more about the early relatives of the tailless forms. There is no assurance at all that it is even ancestral to the Salientia, but the resemblances are striking. The following gives the measurements of the type specimens:
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