76 CONTRIBUTIONS 



to our coast, the transversa and ponderosa of Say. These 

 are from the Tertiary of North Carolina, Virginia and 

 Maryland. 



GENUS PECTUNCULUS. Lamarck. 



P. Broderipii. Plate 3. Fig. 53. 



Description. Shell rather oblique, inflated, inequilateral, 

 nearly straight at dorsal margin, with delicate longitudinal 

 linear ribs, cut by very minute transverse striae ; beaks 

 rather elevated ; hinge teeth arched and very diminutive 

 in the centre ; cicatrices slightly raised ; ^cavity of the 

 shell deep; marginal teeth pointed, small and well defined. 



Diam. .9, Length 1.3, Breadth 1 .4, of an inch. 



Observations. This species is, perhaps, most remarka- 

 able for its small and beautifully pointed marginal teeth, 

 and the straight line of the dorsal margin. The longitu- 

 dinal linear ribs, which diverge from the point of the beak 

 and extend to the margin, are beautifully cut by the fine 

 concentric striae, which interrupt them. This can only 

 be perceived in specimens which are in the best state of 

 preservation. In young specimens, the obliquity does not 

 always exist, and the shell is then equilateral. In perfect 

 specimens, with the assistance of the microscope, the dorsal 

 teeth will be seen to be transversely striate. 



In placing the name of so distinguished a conchologist as 

 that of Mr. Broderip to this species, I have great pleasure. 



