Gastropoda. -7 



The ' Orange-Cowry ' (<'//j>raea aurantium) is worn by chiefs in 

 the Friendly Islands, and is considered the highest order of 

 dignity. Only one small species, Trivia europaea, is found on the 

 British coasts. 



Of the Ovulidae, the most curious is the ' Weaver's-shuttle ' 

 (Radius volva), in which the shell is peculiarly beaked at both ends. 

 It is found living on Gorgonian corals (Gorgoniidae), and some 

 of the smaller species exhibit differences of coloration, resembling 

 the tints of the corals upon which they are found. 



The LameUariidae (Case 37) live on or embedded in Tunicates, in 

 which they deposit their eggs ; the shell is more or less completely 

 covered over by the mantle. 



The ' Violet Snails ' (Ianthinidae) are found floating about in 

 every ocean, excepting in cold regions, with the spire of the shell 

 downwards. They feed upon Jellyfish, and secrete a gelatinous 

 raft, filled with air-bubbles, to the underside of which the eggs 

 are attached. 



The Melayiiidae are freshwater Snails which abound in most 

 tropical and subtropical countries. They are mostly of dark 

 colours, and are found in muddy places. 



The Cerithiidae are chiefly marine forms, some, however, 

 entering brackish water. About five hundred fossil species have 

 been described, some of them gigantic in comparison with any 

 now living. 



The three families Pyramidellidae, Eulimidae, and Entochonchi- 

 dae are known as the Aglossa, as they have no radula. Most of 

 the Eulimidae and all the Entoconchidae are parasitic on 

 Echinoderms, and some are very degenerate in structure. 



The 'Worm-shells' (Vermetidae) are a very peculiar family. 

 Their shells can scarcely be distinguished from the shelly tubes 

 which are formed by certain species of marine worms (e.g. 

 Serpula, &c). They are free and spiral in early life, but after- 

 wards become partly ' unwound ' and generally attached to 

 rocks, stones, &c. Sometimes they form large encrusting masses. 



The ' Screw-shells ' (Turrit ellidae) have elongate, tapering 

 shells. Turritella communis is found on the British coasts. 



The Xenophoridae have the singular habit of cementing to the 

 exterior of their shell stones, pieces of coral, and fragments of 

 other shells ; hence they have been called ' Carrier- shells ', and, 

 according to the kind of material chosen, have been named 

 ' Conchologists ' and ' Mineralogists '. Beyond acting as a 

 disguise, and consequently as a protection, there does not appear 

 to be any special utility in thus adding to the weight of their own 

 shells. The animals do not glide like other molluscs, but scramble 

 along. 



The ' Wing-shells ' (Strombidae) do not crawl like most other 

 Gastropods, but progress by a sort of jerking movement or by 



