Wetter — Kinderhook Fanned Studies. 85 



Pernopecten ?? sp. 



Plate III. f. 5. 



It is by no means certain that this genus occurs in the 

 fauna of the Chonopectus sandstone. The specimen here 

 illustrated resembles it in being a nearly flat, smooth shell, 

 but it differs from Pernopecten in the absence of both the 

 anterior and posterior auriculations. It is of course possible 

 that the ears have been destroyed, but the margin of the shell 

 seems to be uninjured, and if this is the case it cannot be 

 Pernopecten. It is perhaps more probable that this shell 

 should be associated with those called Posidonomya ? am- 

 bigua by Winchell. (See p. 105, pi. IV., f. 18, 19.) 



Leiopteria spinalata (Win.). 



PL III. f. 8-9. 



Pterinea spinalata. Bull. U. S. G. S. No. 153 : 511. 



" Shell rather large, very oblique, becoming distinctly 

 arcuate upwards. Left valve very ventricose, with a tapering 

 incurved beak, closely approximated to its fellow ; body of 

 valve regularly arched along the umbonal slope, from which 

 line it describes a rapid convexity to the anterior margin, 

 sloping more gradually to the ventral margin and becoming 

 gradually flattened toward the posterior ventral angle. The 

 upper boundary of the body is an abrupt descent to the plane 

 of the posterior wing, and sharply divides the two ; posterior 

 wing sloping to the dorsal and posterior borders of the valve, 

 produced above into a slender spine, nearly as long as the 

 posterior end of the shell, with a deep sinuation below. An- 

 terior ear short, saccate, less distinctly divided from the body 

 of the valve. Hinge-line straight, with a long, posterior 

 cartilage facet. Surface marked by irregular wrinkles of 

 growth which become fine striae on the posterior wing, and 

 sharp plications on the anterior slope and auriculation. Right 

 valve smoother and considerably less ventricose, with the 

 posterior wing- surface divided from the body of the valve 

 only by a slight groove." 



Remarks. None of the specimens in the University of 

 Michigan collection are marked as types, but there are five 

 well preserved left valves and four right valves of the species, 

 labeled by Winchell, which agree well with his description and 



