00 PALEONTOLOGY OF NEW YORK. 



mm. Another indivickuil measures 27 iiini. in length, 26 imu. in height, 

 hinge-Hno 18 mm. A right valve referred to this species has a kaigth of 

 20 mm. anil a height of 18 mm., hinge-lini' 17 mm. 



This species differs from any known form of Crenipecten ; it is like 

 Aviculopecten in external form and surface characters, and resembles the 

 recent genus Pecten. 



Mr. Meek compares this species with Aviculopecten Coxantis, Meek and 

 Worthen, from the coal measures of Illinois and Nebraska. It is evident that 

 the crenulations of the hinge have not been previously observed. Except in 

 the hinge crenulations, this form has no other relations with the genus Creni- 

 pecten, and it may be found to belong to some genus ^et undescribed, which 

 will include other species now placed with the Carboniferous forms of Aviculo- 

 pecten. 



In the original descriptidu of the genus, McCoy has not indicated tiie intimate 

 structure of the hinge, and it is not improbable that there are several generic 

 types among the species iiuliidcd in the Carboniferous forms of Aviculopecten. 



The right ami left valves have not been found in connrctiun. but their 

 association, and the absence of similar forms in the same beds, render the 

 identity nearly certain. 



Formation and locality. In the Waverly sandstone near Newark, Ohio. 



