OP CONCHOLOGY. » 



ARCIDiE. 

 TRIGONOARCA, Conrad. 



Description. — Trigonal, ventricose, hinge similar to that of 

 Axincea, a very oblique acute carina margins the posterior cica- 

 trix, and extends, though less prominent, to the apex. 



A very perfect valve of Area Eufalenm, Gabb, from Had 

 donfield, N. J., shows the generic characters of this genus much 

 more clearly than the specimen on which the genus was founded. 

 It evidently connects the genera Axincea, Area and Gueullcea 

 more intimately than the existing genera of ArcidoB. This small 

 bivalve therefore proves to be generically related to Trigonoarca 

 Maconensis, Conrad, figured in outline in the Journal of the 

 Academy of Natural Sciences, Vol. IV., 2d series, pi. 47, fig. 

 20. 



Type Trigonoarsa Maconensis^ Conrad. 



TELLINIDiE. 



CYPRIMERIA, Conrad. 

 Cyprimeria cretacensis, Conrad, [Sanguinolaria.) — Journ. 

 Acad. Nat. Sciences, Vol. IV., 2d series, p. 277, pi. 46, fig. 

 11. 



Dosinia Haddonfiehieusis, Lea. — Proceed. Acad. Nat. Sciences, 

 1861, p. 150. 



AVICULID^E. 



PULYINITES, Defrance. 

 P. ARGENTEA, Conrad. 



Description. — Lower valve flattened or bent outward, sub- 

 stance thin, laminated and nacreous ; hinge with a broad plate, 

 which is terminal and furnished With transverse prominent teeth, 

 flat on their summits ; the series placed in a rectilinear line, but 

 the teeth decreasing in size in consequence of the slope of the 

 dorsal margin ; valve perforated in the umbo, from the upper 

 margin of which opening is a triangular groove running to the 

 apex ; muscular impressions two, one above the other ; the upper 

 one not exactly under the foramen, but a little to the right of 

 a line from the apex to the ventral margin. 



Pulvinites argentea, Conrad. — Journ. Acad. Nat. Sciences, 2d 

 series. Vol. IV., p. 298, pi. 46, fig. 51. 



This interesting bivalve is nearly related to Isogtiomen, Klein, 

 {Ferna, Lam.), and with which when very young it might be con- 

 founded, because in an early stage of growth it has, like that 



