NERITINA. 23 



CLASS II. GASTEROPODA (belly forming the foot) OR 

 UNIVALVES. 



Order I PECTINIBRANCHIATA. 



Family I. NERITID^E. 



Genus. NERITINA. 



N. FLUVIATILIS (inhabiting rivers). 



Ovate, solid, glossy, chequered brown and white and 

 purple ; whorls three ; spire short ; operculum semi-lunar. 



This prettily marked shell is found in many parts of 

 Great Britain attached to stones in running water and 

 canals. It is the most solid of the freshwater shells, 

 and reminds us of its marine cousins, the Littorince, so 

 common on seaweed. 



Family IL- PALUDINID^} (living in marshes). 

 Genus I. PALUDINA. 



1. P. CONTECTA (covered % operculum). 



Conical, diaphanous, fairly glossy, light green, with 

 darker bands of the same colour; whorls seven, very 

 convex ; suture very deep ; mouth almost circular, but 

 angulated above; umbilicus small, but deep and distinct; 

 operculum thin. 



