118 PALEONTOLOGY OF THE EUREKA DISTRICT. 



men as figured by Mr. Meek is like those before me, one of which (plate 

 xiii, fig. 7) varies slightly from his figure and those illustrated by Professor 

 Hall (Pal. N. Y., vol. iv, pi. x, figs. 1, 2.) 



The other variety represented in Nevada, var. perversa, is limited to 

 the Lower Devonian horizon, although found at somewhat widely separated 

 localities. In New York, it is found both in the Upper Helderberg and 

 Hamilton Groups. 



Formation and localities. Devonian limestone, Lone Mountain, 1 8 miles 



/ 



northwest of Eureka, and several localities within the Eureka District, 

 Nevada; also on north end of the Pinon Range, Nevada. 



Genus STROPHOMENA Blainville. 



Strophomena rhomboidalis Wilckens (Sp.). 



For synonyms, see Davidson's Monograph of the British Silurian Brachiopoda, vol. iii, 

 p. 281; and Pal. X. Y., vol. iv, p. 76. 



This widely-distributed species was found in but one locality on Lone 

 Mountain, not being recognized within the limits of the map of the Eureka 

 District. The specimens are of the ordinary character, with rather strong 

 concentric undulations. They are associated with Strophodonta perplana, 

 S. ampla, and Streptorhynchus Chemungensis, var. Pandora. 



The species has been recognized in the Lower Carboniferous of Utah, 

 and at the same horizon in the Spring Mountain Range of Nevada, but not 

 before in the Devonian of the Rocky Mountain. 



Formation and localities. Lower Devonian horizon of Lone Mountain, 

 18 miles northwest of Eureka, Nevada; also in the Lower Devonian, on the 

 north end of the Pinon Range, Nevada. 



Genus STROPHODONTA Hall. 



Strophodonta demissa Conrad (Sp.). 

 Plate ii, figs. 9, 9 a, ft. 



Strophomena demissa Conrad, 1842. Jour. Acad. Nat. Sci. Philad., vol. viii, p. 258, 



pi. xiv, fig. 14. 

 Strophodonta dimosa (?) Owen, 1862. Geol. Surv. Wis., Iowa, and Minn., tab. iii, A, 



fig. 14. 



