174 PALEONTOLOGY OF THE EUREKA DISTRICT. 



width about twice the height; beaks moderately prominent and incurved, 

 situated near the anterior end, which is rather abruptly rounded; basal line 

 slightly sinuate midway; posterior end obliquely rounded, truncate above 

 the lower third, rounding into the basal line and forming a very obtusely 

 rounded angle with the cardinal margin; cardinal line nearly straight and 

 declining towards the anterior end; umbonal ridge prominent, subangular, 

 becoming more rounded toward the extremity of the posterior portion oi 

 the shell. 



Surface showing a few lines of growth. Anterior muscular scar small, 

 semicircular, and near the anterior margin ; posterior scar subcircular, not 

 strongly denned, situated on the postero-cardinal slope, near the margin. 



This species resembles Nyassa recta Hall (Pal. N. Y., vol. v, pt. 1, 

 Plates and Explanations, p. 14, pi. liii, figs. 1-8, 1883) of the Hamilton 

 Group of New York, but differs in the outline of the valves and its less 

 prominent beaks. 



Formation and localities. Lower Devonian; on the west slope of 

 County Peak, Middle to Upper Devonian, at Rescue Hill, west of Rescue 

 Canon, Newark Mountain, and east side of Packer Basin, Eureka District, 

 Nevada. 



Genus GRAMMYSIA De Verneuil. 



Grammy sia minor n. ep. 

 Plate xv, figs. 15, 15 o. 



Shell very small, transversely elongate-ovate; valves ventricose; beaks 

 strongly incurved, situated near the anterior end, which slopes abruptly 

 from the beak with a slightly concave outline to the somewhat sharply 

 rounded end that passes below into the basal line; this, with the exception 

 of a slight sinuosity caused by the median or byssal groove, is transverse 

 to where it rounds up slightly on the posterior margin to meet the oblique 

 line of the upper postero-margin, with which it forms an obtuse angle, 

 giving the posterior end of the shell a pointed appearance; cardinal line 

 straight about two- thirds the length of the valve; umbonal ridge rounded 

 or subangular, postero-cardinal slope abrupt. 



Surface marked by rather strong, rounded concentric ridges and fur- 

 rows that are nearly obsolete on the posterior umbonal slope. 



