CAEBONIFEEOUS SPECIES. 67 



Locality and position. — West side of Buell Valley; Summit Spring Pass; 

 Euby Valley; White Pine Mountains and other localities in Nevada: 

 from a light-colored limestone believed to belong to the upper part of the 

 Carboniferous series of that region. 



Prodxjctus (undt. sp.) 



Plate 7, figs. 6, G a, 6 h. 



Compare Productus Ivesii, Newberry (18G1), Ives' Eeport on the Colorado, 122, pi. ii, 

 figs. 1-8; also Productus Calhounianus, Swallow (1858), Trans. Acad. Sci. 

 St. Louis, I, 180. 



Shell attaining a large size, longer (measuring over the curve of the 

 ventral valve) than wide; hinge apparently not quite equaling the greatest 

 breadth. Ventral valve very gibbous, much produced anteriorl}^, 

 very strongly arched, and provided with a deep, wide mesial sinus that 

 extends from the unbonal region to the produced front,' to which it gives an 

 emarginated appearance as seen from above; most gibbous portion on each 

 side of the sinus, comparatively narrow, with abruptly descending lateral 

 slopes, which converge rather gradually to the beak; ears apparently, nearly 

 rectangular, arched, and wrinkled ; surface ornamented by medium-sized, 

 well-defined, occasionally bifurcating costae, that bear numerous, more or 

 less alternately-an-anged little nodes, each of which was the base of a slen- 

 der spine sometimes apparently attaining a length of nearly three-quarters 

 of an 'inch ; beak comparatively small at the apex, incurved so as to pass 

 within the hinge-line, and, together with the adjacent umbonal region, 

 crossed by small concentric wrinkles, which become stronger on the ears; 

 lines of growth very fine and regular. Dorsal valve somewhat flattened or 

 a little concave in the visceral region, and abruptly cui^ved parallel to the 

 other in front, provided with a mesial ridge corresponding to the sinus of 

 the other valve; surface ornamented with costse similar to those of the other 

 valve, and crossed on the visceral region by small, regular concentric 

 wrinkles; cardinal edge strengthened within by a strong marginal ridge on 

 each side of the short, recurved cardinal process, from the base of which 

 there extends forward a small mesial ridge, which is bifid at its connection 

 with the process. 



Length of one of the largest specimens, measuring over the curve of the 



