76 PALEONTOLOGY. 



In its smooth surface, deep mesial sinus, and strong spines, this species 

 resembles the narrowest varieties of Produdus horridus of Sowerby- Its 

 uniform adult size, however, from widely-separated localities, and through 

 a great thickness of strata, is less than half that of the average size of P. 

 horridus; while it is greatly more produced and elongated in proportion to 

 breadth, and has a proportionally shorter hinge and smaller ears. All its 

 associate fossils in the same beds are also decidedly Carboniferous forms, 

 while P. horridus is a Permian species. 



In some respects, this shell resembles a form described by Professor 

 Swallow, from the Coal-Measures of Kansas, under the name P. costafoidcs. 

 It attains a larger size, however, and is more produced anteriorly ; while it 

 wants the well-defined costae of that shell, being almost entirely smooth, 

 excepting the spine-bases, and the faintest possible traces of a few broad, 

 undefined ridges, sometimes seen descending the anterior slope. It never 

 shows the faintest indications of concentric ridges, or furrows, on the visceral 

 region, or any other part of the surface. 



Locality and position. — Light-colored Carboniferous limestone of Wa- 

 satcli ]\Iountains; Hamilton Butte, Ruby Group; Mahogany Peak, Egan 

 ]\Iountains, and north slope of Moleen Peak, Elko Range, west side of Long 

 Valley, Ruby Group. 



PRODUCI'US MULTISTUIATUS, Meek. 



Plate 8, figs. 3, 3 (I, 3 6, 3 c, 3 rf, 3 e. 



Producliis multlHtriaim, Meek (1800), Proceed. Acad. Nat. Sci. Pliilad., July, 309; 

 and (1870) iu Col. Simpson's Keport Expl. across iLe Great Basin of Utab, 350, 

 pi. 1, figs. 8 a, b. 



Shell of about medium size, much produced ; length of entire speci- 

 mens greater than the breadth, even by direct measurement from the umbo 

 to the produced front, and proportionally still longer, measuring over the 

 curve of the ventral valve ; ears of moderate, or rather large size, some- 

 what triangular, strongly vaulted, and defined by a sinuosity of each lateral 

 margin, which generally makes them less than rectangular at the extremi- 

 ties ; lateral margins rounding anteriorly from the sinuosity in advance of 

 each ear, to the front, which is distinctly sinuous in outline at the middle. 

 Ventral valve extremely gibbous, very strongly arched, and provided with 

 a profound mesial sinus, which extends from near the umbo to the front ; 



