GASTEROPODA. 



Example, P. bilobatum. Upper Lias, Normandy. Fig. 11. 

 Culcareous plates nearly circular or transversely oval ; ante- 



Fig. 11. 



rior border rounded, posterior produced and truncated ; concave 

 above and flattened below ; the two faces have one-half smooth 

 and the other concentrically striated in an inverse direction 

 to each other. 



Fossil, 3 or 4 species. Up. Lias — Cor. Eag. England; 

 Normandy ; Wurtemberg. 



CLASS II.— GASTEEOPODA. 

 Oedee, I. — Peosobranchiata. 

 Family II. — Mueicid^ (see p. 212, &c.). 



The genera included in this family are : — 



Mtjeex, Typhis, Pisakia, TEOPHOisr, Fasciolaeia, Tuebi* 

 NELLA [Cynodonta, Latirus, Lagena), Fusus [Clavella, CJiryso- 

 domus, Pusionella, Tritonidea), FuLGUE, Cominella, Myeis- 

 TiCA, and Lachesis 



Anachis, H. and A. Adams. 



Type, Columbella scalarina, Sowerby. 



Shell like Columbella; ojDerculum elongated, unguiform, 

 nucleus terminal, having close analogies with Pisania. 

 Distribution, 27 species. Tropical America. 



Ptychateactus, Stimpson, 1865, 



Etymology, ptych, a fold ; atradus, a spindle. 

 Type, Fasciolaria ligata, Mighels and Adams. Deep water ; 

 United States. 



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