THE rock shells or murices are among the most beautiful and interesting of all the mollusks or shell fish, and are a favorite among collectors. Their peculiar spiny shells and brilliant colors caused them to be among the first mollusks studied by naturalists and we find them, therefore, described in the earliest works on natural history.

There are about two hundred different kinds of rock shells, mostly confined to the tropical and subtropical seas, although a few are found in temperate climes. The greatest number of these are found about rocks at low water but not a few are inhabitants of waters as deep as fifty fathoms or more. In our own country they are abundant along the coast of Panama, the Gulf of California, Florida and the islands of the West Indies, but the largest number of varieties comes from the Indian Ocean, Japan, the Philippines and Australia. The more brightly colored varieties are from tropical seas, while the dull, plain species are from subtropical or temperate climes.

The murices are peculiar in having their shells ornamented by numerous projections, which vary from long, needle-like spines to simple fluted frills. What these spines and frills are for would probably puzzle the ordinary observer, as they would seem at first sight to be in the way. In some cases they are simply ornamental, but in the main they are protective and enable the animal to escape being eaten by some voracious fish. This is known as protective adaptation and was probably brought about in this manner: the murices, or their ancestors, did not at first have spiny shells, and they fell an easy prey to the fishes. As time went on a few individuals, through some modification of environment, developed small spines or prominences. The animals having these were not eaten by fishes as the knobs and spines caused the fishes pain when swallowed, therefore they preferred the animals with smoother shells. In time this modification caused a weeding-out process, the animals with smoother shells being exterminated and those with spiny shells increasing in numbers and becoming more spiny as one generation succeeded another. This continued until the present time and is going on even now.

Another interesting fact concerning the development of this ornamentation is that the smoother shells inhabit rocky shores where the waves are constantly beating in with greater or lesser violence, while the more spiny individuals live in protected and comparatively still water. This adds additional weight to the theory expressed in the last paragraph, for the fish which feed upon these shells do not, as a rule, inhabit localities where the water is rough, as along a rocky shore, but live abundantly in protected bays and lagoons in which the spiny murices are found.

There are shown on the plate eight species of rock shells, all more or less common. The first one for us to consider may be called Venus' Comb, (Murex tribulus) and is found in China, Japan and the Indian Ocean. It belongs to a group of shells which is characterized by a long snout or canal, and long, pointed spines. The color is yellowish; in one variety the spines are tipped with black.

A shell which is found on the mantel in every household is known as the Branched Rock Shell (Murex ramosus), which is widely distributed, being found in the Red Sea, the Indian Ocean, New Zealand, Australia and the Central Pacific Ocean, and attains a large size, some specimens reaching the length of a foot and weighing several pounds. The aperture is frequently tinged with a deep, beautiful pink. In many households the large shells of this species are used for flower pots, suspended from a hook over the window by a set of chains, and for this purpose they are certainly very ornamental.

The Apple Murex (Murex pomum) is of home production, being found on the shores of Florida and throughout the West Indies. It is not as attractive as the shells just mentioned, but is very common, every collector possessing several specimens in his cabinet.

In the aperture of this species will be noticed a dark brown object which is known as an operculum or door, and its use is to close the aperture when the animal withdraws into its shell, so that the latter may be safe from its enemies. All of the rock shells possess this organ, which is attached to the back part of the animal's foot.

A peculiar and somewhat rare shell is the Horned Murex (Murex axicornis), found in the Indian Archipelago, whose shell is made up of many curiously fluted spines. The Burnt Murex (Murex adustus), is an inhabitant of the Indian Ocean, Japan and the Philippines, and its name, which signifies burned, is well chosen, for all its spines and frills and most of the shell are black in color and look just as though the shell had been scorched. The aperature is often beautifully tinged with pink or dark red.

A common rock shell found in the Mediterranean Sea as well as on the Atlantic coast of France and Portugal and the Canary Islands, is the Purple Murex (Murex trunculus). This is a light brown, three-banded shell about two inches in length and is famous as having been used by the ancients to obtain their beautiful and rich purple dye. On the Tyrian shore these shells were pounded in caldron-shaped holes in the rocks, and the animals were taken out and squeezed for the dye which they secrete. If the animal of one of our common purpuras, a small shell found along the Atlantic and Pacific coasts, be squeezed, it will exude a purple fluid which will stain fabrics a reddish purple. It is probable that much or most of the royal purple of the ancients was obtained from these lowly creatures.

Although the most beautiful shells of this family are supposed to live in the warm, tropical seas of the Indian Ocean, it is nevertheless true that many of the most brightly colored rock shells live in the warm waters of Panama and Mazatlan. The Root Murex (Murex radix) is one of these shells, which attains a length of five inches and weighs several pounds. The shell is white or yellowish-white and the spines and frills are jet black, the two colors producing a peculiar effect. Another beautiful shell from the same locality (Panama) is the Two-colored Murex (Murex bicolor), a shell attaining somewhat larger dimensions than the last. The spines are reduced to mere knobs in this species, there are but a few frills, and only two colors, the shell being greenish-white and the aperture a deep red or pink, plainly showing whence the name, bicolor, two-colored. This shell is collected by thousands at Panama and shipped all over the United States to curiosity stores at summer watering places and other vacation resorts, where they are sold at from a few cents to a dollar each, according to quality.