FOSSILS OF THE DEVONIAN. 125 



The largest specimens from Nevada have a length of 4 mm , and a width 

 of 6 mm , the ventral valve being strongly convex or gibbous and marked by 

 from eighteen to twenty-two strong striae. There is only one cardinal 

 8}>ine preserved; this is bent down and directed outward subparallel to the 

 cardinal margin. 



The specific identification is made with hesitation, as the specimens 

 are somewhat imperfect, and the large adult shells are not present in the 

 collections from Eureka; still the facts in favor of the identification appear 

 to be much stronger than those against it. 



Formation and locality. In the upper beds of the Devonian limestone 

 of the foothills east of Sentinel Mountain and the Sugar Loaf, Eureka 

 District, Nevada. 



Chonetes setigera Hall. 



Strophomena setigera Hall, 1843. Geol. Eep. Fourth District of New York, p. 180, fig. 2. 



Chonetes setigera Hall, 1857. Tenth Ann. Hep. N. Y. State Cab. Nar. Hist., p. 150. Hall, 



18G7. Pal. N. Y., vol. iv, p. 129, pi. xxi, fig. 2; pi. xxii, figs. 1-5. 



This species is associated with the preceding in the same hand speci- 

 mens of limestone. Of its occurrence in the Marcellus shale, Professor 

 Hall says: "This species occurs in the same black shale with C. mucronata, 

 and may be distinguished from it by the more numerous and more fre- 

 quently bifurcating striae, which are likewise more angular. The direction 

 of the cardinal spines, when present, is always a characteristic feature." 



This comparison is equally accurate when applied to the Nevada speci- 

 mens, as the specific characters are similar in the eastern and western shells. 

 Professor Hall gives Meadville, Pennsylvania, as the locality where it is 

 found in the Chemung Group, thus showing its range upward from the base 

 of the Hamilton Group. As far as known, it occurs only in the upper beds 

 of the Devonian, in the Eureka District. 



Formation and locality. In the upper beds of the Devonian limestone 

 of the foothills east of Sentinel Mountain and the Sugar Loaf, Eureka Dis- 

 trict, Nevada. 



