19 4 PALEONTOLOGY OF THE EUEEKA DISTRICT. 



the transversely ovate aperture; a narrow dorsal cariria is distinctly shown 

 on the cast, and, very obscurely, traces of transverse striae. 



This is the largest of the several species occurring in the Devonian 

 limestone of Nevada. Its length is 48 mm ; transverse section midway of the 

 outer volution 30 mm , near the aperture 46 n T 



Formation and locality. Lower horizon of the Devonian limestone, 

 Comb's Peak, Eureka District, Nevada. 



Bellerophon lyra Hall (Pal. N. Y., vol. V, pt. 2, p. 113, pi. xxiii, figs. 1, 17-20). 



A single specimen that corresponds in form and surface markings to 

 this species occurs in the Devonian limestone on the eastern side of the 

 District. It has been slightly worn by exposure to the weather, but not so 

 much as to remove the fine, undulating, revolving striae. 



Bellerophon Leda Hall (Pal. K. Y., vol. V, pt. 2, p. 110, pi. xxiii, figs. 2-16). 



The Nevada form is a little less flattened on the dorsum, and the dorsal 

 carina is more prominent, as are the revolving striae; this, however, is rather 

 the result of a difference in the conditions of preservation than of absolute 

 differences in the shells; the New York specimens usually occurring in the 

 argillaceous shales or shaly limestones have suffered by compression. 



Bellerophon Maera Hall? (Pal. N. Y., vol. v, pt. 2, p. 119, pi. XXV, figs. 9-14; pi. xxvi, 

 figfr. 19-24>. 



A fragment from the higher beds south of The Gate has a thick test 

 thickly studded with rows of pustules in a manner similar to that of B. 

 Mcera of the Chemung Group of the State of New York. The general 

 form of the volutions and dorsal carina also adds to the strength of the 

 comparison 



Bellerophon Pelops Hall? (Pal. 1ST. Y., vol. v, pt. 2, p. 95, pi. xxii, figs. 7-13). 



Associated with B. Leda, there is a form that corresponds to one of the 

 varieties of this species from the Upper Helderberg limestone of the State 

 of New York. The transverse striae of the surface of the body volution 

 bending backward towards the dorsal carina and the expanded aperture 

 show in the Nevada specimen. 



