317 



Bulletin 5 47 



FOSSIL SHELLS. H^ 



NUCULA. 



I. N. IcBvis. PI. X. fig. 5. Transversely elon- 

 gate-subovate, rostrated, nearly smooth. 



Description. Shell compressed, thin, fragile, 

 polished, smooth, slightly wrinkled towards the 

 base : beaks nearly central, hardly prominent be- 

 yond the hinge margin, rounded, approximate: 

 series of teeth subrectilinear, a little arcuated be- 

 hind ; teeth prominent : hinge margin exteriorly 

 both before and behind the beaks rather abruptly 

 compressed : posterior margin rounded : anterior 

 margin somewhat rostrated, the anterior hinge 

 margin rectilinear, very little reflected at tip : hi- 

 tter viargin simple. 



Length nearly half an inch, breadth nearly one 

 inch. 



This shell may be compared with the N. pellu- 

 cida, Gmel. but it is shorter, in proportion to its 

 width, and the beaks are nearer the centre. It 

 is still more closely allied to a recent species of 

 our coast, that has probably been hitherto consi- 

 dered as the rostrata. 



2. N. concentrica. PI. x. fig. 6. Transversely 

 elongate subovate, rostrated, concentrically stri- 

 ated. 



Description. Shell convex : rostrum consider- 

 ably narrowed towards the tip : surface concentri- 

 cally striated with numerous, regular, equidistant, 



[J. A. N. S., Phila., ist Ser., Vol. IV, 1824.] 



