254 PALEONTOLOGY OF THE EUREKA DISTRICT. 
In comparing with Schizodus cuneus Hall, from the Waverly Group 
(Pal. N. Y., vol. v, pt. 1; Plates and Explanations, pl. Ixxv, figs. 27-30), a 
strong resemblance is apparent, the Nevada shell differing only in its more 
robust form and in the strongly arcuate basal and anterior margins. 
Formation and locality—Lower portion of Lower Carboniferous lime- 
stone, in the canon northeast of Pinto Peak, Eureka District, Nevada. 
GASTEROPODA. 
Genus PLATYCERAS Conrad. 
Platyceras occidens, n. sp. 
Plate xxiv, figs. 9, 9a. 
Shell obliquely subconical, apex minute and strongly incurved, the 
nucleus making about one volution and then rapidly expanding; the dor- 
sum is somewhat abruptly rounded but not carinate; the right side is gently 
and evenly convex to the rounded angle formed by the union with the 
front; the left side is more abruptly convex, and curves forward impercep- 
tibly into the anterior surface. Aperture subtriangular in outline with the 
peristome sinuous. 
Surface marked by fine, well-defined, undulating strize of growth. 
This is a small and very pretty species. It may be compared with 
some forms of Platyceras carinatum Hall (Pal. N. Y., vol. v, pt. 2, p. 5, pl. 
ii, figs. 12-29) of the Devonian. 
Formation and locality—Lower portion of Lower Carboniferous lime- 
stone, in canon directly south of a small conical hill on east side of Secret- 
eanon-road Canon, Kureka District, Nevada. 
Platyceras Piso, n. sp. 
Plate xxiv, figs. 7,7 a, b. 
Shell obliquely and strongly arcuate; apex minute, incurved, making 
about one volution; body-whorl expanding rather rapidly at first and then 
very gradually to the aperture; dorsum rounded; sides and dorsum with 
seven or eight slight longitudinal plications; aperture broadly subovate 
with the peristome sinuous. 
