FOSSILS OF THE DEVONIAN. 



163 



Genus CRYPTONELLA Hall. 



Cryptonella ? circula, n. sp. 



Plate xv, figs. 2, 2 a, 6. 



Shell small, subcircular or ovoid. The depth of the two valves, in 

 uncompressed specimens, is equal to one-half the length of the shell. 



Ventral valve moderately convex, most prominent about one-third the 

 distance from the apex to the front, from which point it slopes regularly to 

 the margins and beak; a slight depression of the front margin is the only 

 indication of a mesial sinus; beak scarcely incurved, truncated by a small 

 round foramen, that, in the absence of the deltidial plates, opens below into 

 a rather large deltoid fissure that has a narrow, flattened, area-like space on 

 each side. Dorsal valve somewhat shorter than the ventral and subequal 

 in convexity with it. Beak very small and not perceptibly incurved. 



Surface marked by fine concentric striae. Shell structure punctate. 



Dimensions: the largest shell, in a collection of thirty specimens, has 

 a length of 9 mm , breadth of 8.5 mm , and depth of the two valves of 4.5 mm . 



The species is referred to the genus Cryptonella, from its general form, 

 the character of the beak of the ventral valve and the punctate shell struc- 

 ture, the latter character shown on one of the silicified specimens. With 

 these characters the reference is provisional, as the internal features are yet 

 undetermined. 



Formation and locality. Devonian limestone ; Lone Mountain, 1 8 miles 

 northwest of Eureka, Nevada. 



Cryptonella Pinonensis, n. sp. 

 Plate iv, figs. 4, 4 a, 6. 



Shell subovate; widest about the middle; valves about equally convex; 

 rounded to slightly transverse in front. 



Ventral valve regularly arcuate, most convex midway; beak elevated, 

 slightly incurved, and truncated by a small rounded foramen bounded on the 

 lower side by two rather prominent deltidial pieces; the slopes from the beak 

 are abruptly deflected on the sides down to the cardinal margin. 



