FOSSILS OF THE CABBONIFEKOUS. 



253 



Schizodus curt i forme, n. sp. 

 Plate xxii, figs. 3, 3 a. 



Shell small, subrhomboidal, moderately convex; posterior dorsal region 

 back of the umbonal ridge compressed and cuneate; umbonal slope dis- 

 tinctly angular from the beak to the postero-basal margin; anterior slope 

 rather abrupt to the anterior margin. Beak elevated, incurved, and situated 

 a little anterior to the center. 



Surface of the cast with a few indications of concentric lines of growth. 



Interior characters unknown. 



Dimensions: height, 1.5 cm ; width, 1.75 cm ; convexity or depth of right 

 valve, .5 cm . 



This little species is related to Schizodus curtus M. and W. (Geol. Surv. 

 111., vol. v, p. 582), and S. Rossicus De Vern. (Russ. and Ural Mts., p. 309), but 

 can scarcely be referred to either specifically. 



Formation and locality. Lower portion of Lower Carboniferous lime- 

 stone in canon directly south of a small conical hill on east side of Secret- 

 canon-road Cafion, Eureka District, Nevada. 



Schizodus Piutoensis, n. sp. 

 Plate xxii, figs. 2, 2 a. 



Shell about the average size of species of the genus; outline obliquely 

 subrhomboidal; base strongly arcuate; umbonal slope distinctly angular, 

 with the posterior side flattened; general surface moderately convex, curv- 

 ing evenly over the central portions anterior to the umbonal angle and then 

 more abruptly down to the anterior margin. Beaks elevated, incurved, and 

 placed on the anterior third of the shell. 



Surface of cast showing a few lines of growth. 



Dimensions: height, 2 cm ; width, 2.25 cm ; convexity or depth of left 

 valve, 0.5 cm . 



Some of the examples are more oblique, and have the appearance of 

 being more erect, owing to the greater curvature of the basal margin. This 

 is shown in the illustration of the right valve. 



