172 PALEONTOLOGY OF THE EUREKA DISTRICT. 



Genus NUOULA Lamarck, 



Nucula Rescuensis, n. sp. 



Plate xv, fig. 9. 



Shell small, broadly subovate, moderately convex; height to length 

 as four to five; beaks not very prominent, about one-fifth the length from 

 the broadly rounded anterior end; basal line broadly and uniformly curved; 

 posterior end more sharply curved, and with the. upper slope meeting the 

 nearly straight hinge-line at an obtuse angle; posterior umbonal slope 

 prominent and subangular. 



Surface, in the cast, shows evidence of concentric lines of growth 

 where the cast is very perfect, otherwise it is smooth. 



Formation and locality. Middle to Upper Devonian horizon; Rescue 

 Hill, west of Rescue Canon, Eureka District, Nevada. 



Nucula, sp. ? 



Among the collections from Rescue Hill a number of casts of a larger 

 species of Nucula than N. Eescuensis occur. Their form is much like that 

 of N. Niotica of the Upper Helderberg Group of New York, but without 

 some knowledge of the outer shell it is scarcely possible to determine 

 whether it is that species, or a new form allied to some of the Devonian or 

 Chemung species of New York. 



Genus DYSTACTELLA Hall. 



Dystactella insularis, n. sp. 

 Plate xv, fig. 8. 



Shell transversely elongate-ovate, the length and height as two to 

 one; valves moderately convex; anterior end contracted and sharply 

 rounded at the extremity; basal line gently arcuate; posterior end some- 

 what broadly rounded, the extremity coming above a line drawn through 

 the transverse center of the shell; cardinal line a little curved; beaks 

 depressed. 



Surface of cast marked by a strong anterior muscular scar; posterior 

 scar not observed. 



