GASTEKOPODA. 



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

 Calcareous 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. Rag. England; 

 Normandy ; Wurtemberg. 



CLASS II.— GASTEROPODA. 



Order I. — Prosobranchiata. 



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



The genera included in this family are : — 



Mtjrex, Typhis, Pisanta, Trophon, Easciolaria, Turbi- 

 NELLA (Cynodonta, Latirus, Lagena), EUSTJS (Clavella, Chryso- 

 domus, Pusionella, Tritonidea), EuEGUR, Cohinella, Myris- 

 tica, and Lachesis 



Anachis, H. and A. Adams. 



Type, Columbella scalarina, Sowerby. 



Shell like Columbella; operculum elongated, unguiform, 

 nucleus terminal, having close analogies with Pisania. 

 Distribution, 27 species. Tropical America. 



Ptychatractus, Stimpson, 1865. 



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

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

 United States. 



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