LAMELLIBEANCHIATA FROM THE EOCENE MARLS. 227 



nature. In some lights it presents the appearance of a cast of an oyster, 

 while in the position in which it was figured by Mr. Conrad it may readily 

 be viewed in the light of an Avlcula=:Ptena. But after studying the 

 specimen and examining it in every jjosition I liave come to the conclusion 

 that it is only a fragment of the outer volution of one of the large nodose 

 Fasciolaria-Wke shells common in the same beds. If one hold the specimen 

 in a position so as to bring what Mr. Conrad interpreted as the extremity of 

 the posterior hinge-line to the bottom of the specimen, this is at once seen 

 to be the true interpretation of the fragment, that part being a portion of the 

 beak or rostral portion of the shell, and the protuberances, which in the 

 Avicula interpretation represent the beak and anterior lobe or wing, are 

 only two of the nodes on the body of the volution. The name Avicula 

 annosa Conrad ought therefore to be dropped from zoological nomenclature. 

 The specimen was from Shark River, and came from the upper layers 

 of the marl at that place. 



NUCULID^. 



Geuus NUCULA Lam. 



Nucula Circe, u. sp. 

 Plate XXIX, Fig. 12. 



Shell rather above a medium size, very broadly ovate or subtriangu- 

 larly-ovate in outline, with subcentral beaks, and the hinge-line sloping 

 from it nearly equally on each side, inclosing an angle of about 110°. 

 Posterior side of the hinge longest and somewhat arcuate, containing four- 

 teen teeth, with considerable space near the beak unseen, probably contain- 

 ing about six additional ones. Teeth regularly increasing in size po.steri- 

 orly. Anterior side not observed ; basal line gibbous in the middle, leaving 

 the anterior and posterior ends nearly equally pointed. Muscular imprints 

 small, but moderately distinct. Surface of the shell marked by fine radiat- 

 ing strise, most strongly marked on the anterior half of the valve. 



The only specimens of the species observed are flattened by compres- 

 sion, and possibly somewhat distorted also, although of this there is no direct 

 evidence. The valves appear to have been quite convex, although not so 



