GASTROPODS. 



379 



narrow, with three rows of teeth ; the central tooth having three principal cusps 

 or spines, and other secondary denticles, and the laterals being simple. The horny 

 operculum is variable, having either a lateral or terminal nucleus. The shells 

 exhibit much diversity of form in the different groups. Murices are carnivorous, 

 feeding upon other molluscs, both gastropods and bivalves. In the typical genus 

 Murex the animal, as it increases in size, produces at intervals beautiful foliations 

 or spine-bearing ridges, nearly always three or more on a whorl, which are some- 

 times continuous up the spire ; the siphonal canal being sometimes remarkably long 

 and slender, almost closed and nearly straight. In this group many of the species 

 are armed with numerous long spines upon the ridges ; M. tenuispina from the 

 Indian Ocean, Philippine Islands, and neigh- 

 bouring localities, being a striking example. In 

 the section Chicoreus the shells are strong, with 

 three beautifully branched ridges, and the canal 

 shorter than in the preceding group ; M. ramosus, 

 a large and abundant species from the Red Sea, 

 Indian Ocean, Polynesia, etc., and the beautiful 

 M. palma-rosce, from the Philippines, being 

 examples. The species of Muricantha are like 

 Chicoreus in form, but with numerous varices. 

 The west coast of Tropical America and West 

 Africa produce some of the largest and hand- 

 somest species. Of all the group, perhaps none 

 surpass in beauty of construction some of the 

 forms of Pteronotus ; M. lobbeckei, from the China 

 Sea, which is of a uniform delicate rose -pink 

 tint, and ornamented with elegant fluted frill- 

 like varices, being pre-eminently beautiful. There 



are. several other groups, containing a number of species of considerable interest, 

 which cannot be further referred to in this account. Some mention, however, must 

 be made of the dye which can be extracted from the animals of this family. 

 Species of Murex and probably of Purpura — a genus referred to subsequently 

 — were both employed in ancient times in the manufacture of the Tyrian purple. 

 The dye was obtained from a white vein at the upper part of the neck of the 

 mollusc. When first extracted, it is of the colour and consistency of cream, 

 but subsequently changes, on exposure to light, to the deep purple tint. The 

 common British Purpura lapillus affords similar dye. Its scarcity and the 

 use of cochineal, and other dyes, render it valueless as a commercial product. 

 Murex erinaceus, the only British species, is common on oyster-beds, to which it 

 is destructive. All the forms yet referred to have a somewhat roundish or ovate 

 operculum, with the nucleus terminal or subterminal, whereas in those which 

 follow (Purpurinaz) it is lateral. All the members of the genus Purpura are 

 furnished with strong, heavy shells, suitable for protecting the inhabitants from the 

 rough usage of the sea upon the rocky shores they mostly inhabit. They range from 

 the Arctic to the Antarctic regions, the handsomest species coming from tropical 

 seas, The fry of several species are pelagic, and swim at the surface of the water. 



animal OF Murex. b, Gill ; b', Osphradium, 

 or olfactory organ ; p, Purple-gland, 



