180 PALEONTOLOGY OF THE EUREKA DISTRICT. 
Lias (Pictet. Traité de Pal., Atlas, pl. Ixxxii, fig. 14), there is a striking 
resemblance. 
Formation and locality—lLower Devonian of Atrypa Peak, Eureka Dis- 
trict, Nevada, and also at the same horizon on Lone Mountain, 18 miles. 
northwest of Eureka, Nevada. 
Genus MICRODON Conrad. 
CYPRICARDELLA Hall. 
Microdon (C.) macrostriatus, n. sp. 
Plate v, fig. 5. 
Shell transverse, broadly subovate. General surface depressed, very 
slightly convex. Hinge-line more than half as long as the shell. Beaks 
small and situated on the anterior quarter of the shell. 
Surface marked by strong concentric lines of growth, seven in a dis- 
tance of 12™ on the central portion of the shell. 
Dimensions: height, 2™; length about 4°”. 
In general form this species is not unlike Microdon complanatus Hall 
(Pal. N. Y., vol. v, pt. 1, Plates and Explanations, pl. Ixxiv, figs. 14-19). 
The beaks are more anterior and the surface strize more like lines or short, 
sharp undulations of growth than fine striz. 
The anterior half of the shell is preserved on one specimen, the out- 
lined portion of fig. 5 being taken from another, in which the shell in front 
of the beaks is broken away. 
Formation and locality—Lower Devonian of Atrypa Peak, Eureka Dis- 
trict, Nevada; also at the same horizon on Lone Mountain, 18 miles north- 
west of Eureka, Nevada. 
Genus ANODONTOPSIS McOoy. 
Anodontopsis amygdaleeformis, n. sp. 
Plate xv, figs. 7, 7a, b. 
General outline obscurely subtrigonal, moderately convex; slope from 
below the beaks to the anterior extremity slightly concave, and from this 
