122 A Guide to the Zoological Collections in the 



and are generally predaceous. The following are the prin- 

 cipal families : — 



ist Family, Strombidse [Cases 148B— 150A]. 



*' Wing shells" and "Scorpion shells". Among the 

 members of this family the shell of the adult usually 

 differs very considerably from that of the young. In the 

 young it usually has the form of a simple close-coiled 

 spiral cone, but in the adult the outer lip of the mouth of 

 the shell generally becomes greatly expanded in the form 

 either of a simple wing [Strombus), or of a wing festooned 

 with great spreading curving claws [Pteroceras): a series 

 of specimens of Pteroceras, in Case 149C, shows this 

 difference between the young and the adult shell in its 

 most marked degree. The spirit specimen of Rostellaria 

 delicatula, placed above Case 150, shows the characters 

 of the typical animal, with its long snout and its long 

 cylindrical foot for hopping. Observe the characteristic 

 small horny operculum in situ on the foot. 



2nd Family, Aporrhaidge [Case 150B]. 



A small family of Wing shells, no member of which is 

 known to occur in Indian Seas. 



3rd Family, Dolidae [Cases 150 C — 15 iB]. 



" Tun shells", " Helmet shells", " Fig shells". 



In this family the shells are large and inflated, with 

 the whorls ribbed or varicose, and the peritreme deeply 

 notched in front : they are sometimes remarkably thin and 

 light, and sometimes {Cassis) remarkably thick and heavy, 

 especially at the lip. The thick shells of Cassis are used 

 in the manufacture of cameos. 



The animals generally hare a very large foot. In 

 Dolium and its allies there is no operculum. 



4th Family, Tritonidae [Cases 151B — 152C]. 



" Trumpet shells". 



The Tritons are for the most part tropical, and reach 

 their maximum in the Eastern Seas. The shells have 

 usually a prominents pire and numerous ribs or varices, 



