COLEOPTEEA— HTDROPHILID^. 515 



rounded and not acutely pointed. Distinct striation of the elytra is rare in 

 Tropisternus, but it scarcely seems possible to refer this species elsewhere. 



Length of elytra, 6.5"™ ; breadth of combined elyira, 5""°. 



Green River, Wyoming. One specimen, Nos. 3989 and 4084. 



Tropisternus saxialis. 



PI. 8, Fig. 2. 



Tropisternus saxialis Soudd., Bull. U. S. Geol. Geogr. Surv. Terr.. IV, 7f)9-760 (1878). 



One specimen and its reverse, found by me in the Green River shales, 

 represents a species of Tropisternus nearly as large as T. binotatus Walk, 

 from Mexico. The large size of the head and the shortness of the prothorax 

 are doubtless due to the mode of preservation, the whole of the head, 

 deflected in life, being shown, while the thorax is in some way foreshort- 

 ened. In all other respects it agrees with the Hydrophilidge, and especially 

 with Tropisternus, having the form of the species mentioned. The head is 

 broad and well rounded, with small, lateral, posterior eyes. The thorax is 

 much broader and much more than twice as broad as long, with rounded 

 sides, tapering anteriorly, the front margin broadly and rather deeply con- 

 cave, the hind border gently convex ; the scutellum is large, triangular, a 

 little longer than broad. The surface of the thorax and elytra is appar- 

 ently smooth ; at least no markings ar3 discoverable, excepting the line of 

 the inner edge of the inferior margination of tlie sides of the elytra, which 

 appears through the latter, as do also the abdominal incisures and the hind 

 femora and tibiae. These legs are longer and slenderer than in T. bino- 

 tatus, the femora extending beyond the sides of the abdomen, and the tibiae 

 are armed beneath at tip with a pair of slender spines, which together with 

 the tibia? are about as long as the femora. 



Length of body, G.65""° ; of elytra, 4.45'"" ; breadth of middle of body, 

 3.25°'"; length of hind femora, 2"""'; of hind tibite, L25'"'°. 



Green River, Wyoming. One specimen, Nos. t023 and 4027. 



HYDROCHUS Germar. 

 Hydrochus amictus. 



PI. 1, Fig, 47. 



A single fragmentary elytron indicates a species of abont the size of 

 H. subcupreus Rand., and in general resembling it. The figure does not 



