FOSSILS OF THE CARBONIFEROUS. Zo 
to Streblopteria laevigata 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. 9a) 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- 
canon-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. sp. 
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 
