FOSSILS OF THE CARBONIFEKOUS. 



231 



to Streblopteria Icevigata McCoy (Brit. Pal. Foss., p. 482), the type of the 

 genus. The form is also that of species referred to the genus Pernopecten, 

 but in a large number of examples I have not been able to find the crenu- 

 lated hinge area characteristic of that genus; the species agrees more closely 

 with Streblopteria in other characters. The smaller shells resemble Pecten ? 

 pusillus of the Permian (see Mon. Perm. Foss., England, p. 153), but differ 

 in having a longitudinally striated surface. 



Streblopteria tenuilineatus M. and W. (Geol. Surv. Ill, vol. ii, plate xxvi, 

 fig. 9 a) is the only American species that has been referred to the genus. 

 It differs very materially in form and surface characters from the species 

 under consideration. 



Formation and localities. Lower portion of the Carboniferous Group in 

 the canon north of Pinto Peak; on the west slope of Richmond Mountain, 

 and in the canon south of a small conical hill on the east side of Secret- 

 caflon-road Canon, Eureka District, Nevada. 



Genus CRENIPECTEN Hall. 



The genus Crenipecten is described by its author as "Like Aviculopec- 

 ten in form, hinge furnished with a series of small cartilage pits throughout 

 its entire length." Example, Crenipecten Leon and C. crenulatus (Pal. N. Y., 

 vol. v, pt. 1, 1884). 



The study of the species referred to Aviculopecten from the Eureka 

 District shows but one species that has such a hinge. A. affinis, A. Eure- 

 kensis, A. peroccidens, A. Haguei have a flattened hinge, but in none of the 

 examples of those species have we detected any vertical ligamental pits as in 

 Crenipecten. 



, Crenipecten Hallanus, n. np. 



Plate viii, figs. 7,7a-c. 



Shell rather above medium size; outline, exclusive of the ears, sub- 

 orbicular. General surface moderately convex. Hinge-line and greatest 

 width of the shell as 4 to 5 ; 5 to 6 in two examples. Anterior ear smaller 



