233 



Ostrea continued. 



caUifera. . ovate-rotund, a thick callus near the base ; rather 



eared, excavated internally. . Rocquencourt. 

 0. hippopus, Annales du Mus. 

 brevialis. . rotundato-trigonal, base rather pointed, very thick ; 



ligamental canal produced, apex bowed on one side. . 



3 inches. 

 scalar ina. . oblong, reduced toward the base, with transverse, 



bowed, rather distant, step-like rugae. . 2 inches. 

 edulina. . reduced at the base, with imbricating, undulating la- 

 mellae, upper valve fiat. 

 bellovacina. . oblongo-cuneated, rounded upwards ; larger valve 



grooved at the base radiatedly. 

 widtilamellata. . oblong, apex dilated, rather bowed, thick ; with 



numerous imbricated, depressed lamellae. . 3| inches. 

 linyuatula. . ovato-spathulated, oblique, rather flat; lower valve 



rostrated. 

 creniilata . . oval, depressed, slightly lamellated, crenulated ; 



chiefly on the inner margin. . size of 0. edulis. 

 cucullaris. . cuneato-spathulate, base rostrated. 



O. cochlearia, Annales du Mus. 

 resicularis. . semiglobose, base retuse, smooth ; lower valve ven- 



tricose ; upper plano-concave. . Meudon. 

 bifiuriculafa. . semiglobose, base truncated, biauriculated ; lower 



valve very ventricose ; upper valve flat, operculifonn. . 



2^ inches. 

 rjbliqua. . obliquely ovate, smooth ; lower valve ventricose ; 



upper valve flat ; hinge very short. 

 linyularis. . elongate, sublinear, flat, narrow towards the base, 



lamellae compact. . 2 inches. . Mons. 

 squama. . ovato-trigonal, flat, but rounded upwards ; concentric 



transverse rugae ; with internally decumbent cylindraceous 



tubercles. . size of a finger nail. 



anrtmialis. . suborbicular, thin, smooth, convex beneath, up- 

 wards flatter. 

 pseudo-chama. . irregularly orbiculate, ligamental pit narrow, 



very oblique. . 2 inches. 

 cyathula. . suborbiculate, with imbricated lamellae, lower valve 



concave, margin crenulated. . 1 inch. 



deformis. . deformed, subdepressed on one side, very irregular. 

 uncinata. . semiorbiculate, hooked, depressed ; a lamellous sinus 



on one side. 



Vulsella. 



deperdita . . oblong, sublingulate, convexo-depressed ; striae 

 transverse, concentric ; base retuse. . Grignon. 



Placuna. 



pectinoides, . obliquely trigonal, flat upwards ; radiated with 

 costellae, a little convex beneath. 



H h. 



