1 14: PALEONTOLOGY OF THE EUKEKA DISTRICT. 



Formation and locality. Lower. Devonian of Brush Peak, Eureka Dis- 

 trict, and at the same horizon at Lone Mountain, 18 miles northwest of 

 Eureka, Nevada. 



Fholidops quadrangularis. n. sp. 

 Plate ii, fig. 7. 



Shell broadly oval, or subquadrangular ; moderately elevated. Sides 

 nearly straight, which gives the quadrangular outline to the shell. Apex 

 eccentric and a little elongate. Slope from the apex to the margin uniform. 

 Surface marked by irregular, not very prominent lamellose striae. Substance 

 of shell calcareous. Dimensions: Breadth, f.5 mm ; length, about 6.5 mm . 



This species is unlike any described form known to us, and although 

 only represented by a single valve showing the exterior, it is too well marked 

 to be confused with any species from the Eastern United States. 



Formation and locality. Lower Devonian at Lone Mountain, 1 8 miles 

 northwest of Eureka, Nevada. 



Genus ORTHIS Dalman 



Orthis McFarlanei Meek. 



Orthis Me. Farlanei Meek, 1868. Trans. Chicago Acad. Sci., vol. i, p. 88, pi. xii, figs. 1 a-h. 



This large species is so strongly marked by its peculiar form that the 

 identification is rendered very satisfactory, although based on imperfect 

 specimens. Its short hinge line, great convexity of the dorsal valve, and 

 narrow umbonal region give it the appearance of Pentamerus galeatus, as 

 mentioned by Meek. The Nevada specimens show the fine radiating- striae 

 and minutely punctate surface with great distinctness, as in the original types 

 of the species from the Mackenzie River Basin, British America. Mr. Meek 

 states that he had seen specimens which he believed to be identical with 

 this species from the Devonian of Iowa and Illinois. 



Formation and locality. Lower horizon of the Devonian limestone, west 

 slope of County Peak, Eureka District, Nevada. 



