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AMERICAN JOURNAL 



cealed when in place under the umbo, to "which it is attached by 

 the flat incurved side. The breaking of the valve on the beach 

 has freed the tooth in an entire condition, and it has been 

 thought to be an ApJysia., which it resembles. The inclosed or 

 tubular part is represented much too long in the figure. 



LAGENA, Bolten. 



L. TiNCTA, Conrad (PoUia.) Proc. Acad. Nat. Sci., vol. iii, p. 

 25, pi. 1, fig. 9. 



Cretaceous Species. 



^ORA, Conrad. 



Hinge Character. — Right valve — three diverging cardinal 

 teeth, posterior one bifid ; cardinal plate broad, deeply channelled 

 anteriorly, with a compressed lateral tooth in the middle of the 

 channel ; plate deeply channeled posteriorly. Left valve with 

 three diverging cardinal teeth, the anterior one v-shaped, ob- 

 lique ; one distant anterior lateral tooth with a channel above, 

 parallel with the cardinal margin ; nympha crenulated on the 

 upper margin ; a distant narrow channel on the posterior hinge 

 plate; pallial sinus deep, reaching to a point in a line with the 

 posterior extremity of the posterior cardinal tooth ; rounded and 

 somewhat ascending;. 



This genus is nearly related to the Eocene genus Isodoma, 

 Desh. It diifers in having three teeth in the right valve instead 

 of two bifid teeth, and in having no lateral tooth posteriorly on 

 the left valve, but a narrow pit in place of a tooth. It has also 

 a much wider hinge plate and a crenulated nympha. The v- 

 shaped tooth on the left valve is a very peculiar and distinctive 

 character. 



M. CRETACEA, Conrad. PI. 3, fig. 8. ' 



Description. — Subtriangular, subequilateral, convex ; end 

 margins acutely rounded; umbo slightly prominent; lunule 

 lanceolate, slightly defined by an impressed line ; ventral margin 

 rounded. 



Locality. — Haddonfield, N. J. 



TENEA. 



Hinge Character. — A v-shaped tooth under the apex of the 

 left valve, the anterior lobe of which is continued along the 

 margin anteriorly, forming a long, deep pit above it ; one distant 

 ver}^ oblique cardinal tooth posterior to the apex. Right valve — 



