172 



KEW YORK State museum 



from the body of the shell, extremity rather pointed, posterior 

 margin sinuate in joining the shell. Both ears ornamented by 

 radiating striae crossed by striae which, on the anterior ear, are 

 sharp and high, giving it a cancellated appearance. The sculpturing 

 of the shell is somewhat similar to that of the ear. The radiating 

 costae two ranked, the smaller ones interpolated between the larger, 

 37 in all, crossed by concentric lamellae which are highly vaulted 

 on crossing the ridges as shown in the molds. Ridges rather sharp 

 and about as broad as the furrows except on posterior region where 

 the latter are wider. 



Aviculopecten lyelli Dawson. Above, two left valves and one right ; below, enlargements 

 of the hinge. Cape le Trou, Grindstone I. 



Dimensions. Length of hinge, 12.75 1^11^ 5 length of shell, 17 mm: 

 height, 19 mm; 6 or 7 striae in 5 mm; angle of beak about 90°. 



Remarks. The specimens figured and described here are some- 

 what undersized. They are closely related to a species from the 

 Knobstone of Indiana but differ in the relative breadth of the ribs, 

 size of the shell, etc. There is a cavity beneath the beaks of our 

 casts, but it is difficult to determine its true character. 



Aviculopecten acadicus Hartt? 

 Cf. Aviculopecten acadicus Hartt. Dawson's Acadian Geology, 

 p. 307, fig. 114, 1878. 



Shell small, convex ; ears not well developed ; beak sharply pointed. 

 Anterior ear sharply separated from the shell, posterior ear not so 

 distinct from it. About 25 radiating costae are shown, separated by 

 wide interspaces and crossed by concentric lines or laminae which 

 are raised on the costae making them appear nodose or the shell 

 reticulated. 



