90 
PALAEONTOLOGY OF NEW YORK. 
mm. Another individual measures 27 mm. in length, 26 mm. in height, 
hinge-line 18 mm. A right valve referred to this species has a length of 
20 mm. and a height of 18 mm., hinge-line 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 Coxams, 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 yet undescribed, which 
will include other species now placed with the Carboniferous forms of Aviculo¬ 
pecten. 
In the original description of the genus, McCoy has not indicated the intimate 
structure of the hinge, and it is not improbable that there are several generic 
types among the species included in the Carboniferous forms of Aviculopecten. 
The right and left valves have not been found in connection, 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. 
