ii8 A Guide to the Zoological Collections in the 



of long pointed many-whorled spires, the lip "of which is 

 often notched and channelled, and they are closed by a 

 horny operculum. 



yth Family, MelanidSB [Cases 137 — 139B]. 



A large family of freshwater mollusks abounding through- 

 out the warmer regions of the world. The shells are 

 spiral turrets, often of great length, and are usually 

 covered with a thick dark-coloured epidermis, and closed 

 by a horny operculum. Very commonly the top of the 

 spire is eroded and decollated, but often [e.g.^ Faunus) 

 is quite perfect. The animals appear to prefer muddy 

 water, and are herbivorous. 



8th Family, Pyramideilidse [Cases 140A, B]. 



The shells in this family are most usually long acutely- 

 pointed many-whorled spires, with the lip often notched 

 and slightly channelled. The animals are marine, and 

 are probably predaceous. Operculum horny. 



9th Family, TurrltelUdse [Case 140X]. 



The " Screw Shells " are marine and are widely dis- 

 tributed. In the Turritellidx proper the shell is an 

 elongate beautifully tapering spire: in the Cdscid% it is a 

 spiral disk in the young stage, but in the adult, by the loss 

 of the spire, it becomes a simple tube : in the Vermetidse 

 also it becomes in the adult a loosely and irregularly 

 twisted tube, much like a worm-tube. The shells are 

 usually furnished with a horny operculum. 



loth F'amily, Xenophoridse [Case 140X]. 



The " Carrier-shells " are marine, and have the remark- 

 able habit of strengthening and protecting their own shells 

 with the dead shells of other species of Mollusca, the 

 protective pieces being arranged with beautiftd regularity 

 round the edjjes of the whorls. The foot is also remark- 



