FOSSILS OF THE TEIASSIC FORMATION. 281 



more and better material shall have been examined, but at present we hesi- 

 tate to so consider it. 



Formation and locality. — In limestone of supposed Triassic age, asso- 

 ciated with Spiriferina Homfrayi and Terebratula Humholdtensis Gabb., near 

 Dun Glen Pass, Pah-Ute Eange, Nevada. Collected by Arnold Hague, esq. 



BEACHIOPODA. 



Genus SPIRIFERINA D'Orb. 

 Spirifekina Homfkayi ?. 



Plate VI, fig. 18. 



? Spirifer Homfrayi Gabb, Geol. Sur. Cal., Pal., vol. 1, p. 35, pi. 6, fig. 38. 



It is with considerable hesitation that we refer to the above species 

 some very imperfect fragments in the Dun Glen collections. They con- 

 sist of two imperfect dorsal valves, and some still more fragmentary ventrals; 

 the latter altogether too imperfect for illustration. The dorsal valves are 

 depressed-convex, with slightly rounded cardinal extremities; the mesial 

 fold is simple, broad, and rounded, the front forming a little more than one- 

 fourth of the entire width of the valve, measured along the hinge-line. The 

 sides of the shell are each marked by seven or eight simple, scarcely angu- 

 lar plications, rapidly decreasing in size from the middle outward; front 

 margin nearly semicircular in outline. The ventral valve has been erect 

 and pointed at the beak; the plications appear more angular than those of 

 the dorsal, and the area of considerable height. 



The specimens are badly exfoliated, thus rendering the surface-charac- 

 ters obscure. The texture of the shell cannot be distinctly made out, but 

 appears to have been punctate, and for this reason we have classed it 

 under the genus Spiriferina, although it may possibly not be properly 

 referred. 



Formation and locality. — In dark-colored limestone of Triassic age, one 

 and a half miles south of Dun Glen Pass, Pah-Ute Range, Nevada. Col- 

 lected by Arnold Hague, esq. 



Spirifera (Spiriferina ?) Alia n. sp. 



Plate VI, fig. 17. 



Shell of medium size, transversely broad-ovate ; the width about one- 



