32 NON-MARINE FOSSIL MOLLUSC A. 



Iu addition to the six species last-mentioned, the three which are de- 

 scribed in the following paragraphs for the first time, have been discov- 

 ered in the Laramie strata of South Platte Valey, Colorado, since the 

 former were published. 



Gorbicula berthoudi (sp. nov.), Plate 21, figs. 1, 2, and 3. — Shell 

 very large, subtrigonal iu marginal outline, moderately gibbous: front 

 concave immediately in front of the beaks; front margin regularly 

 rounded ; basal margin broadly rounded ; posterobasal margin ab- 

 ruptly rounded up to the postero-dorsal margin, which latter margin 

 slopes obliquely downward with a gentle convexity from between the 

 beaks; hinge strong; all the teeth well developed, the lateral ones espe- 

 cially being long and large and crenulated upon their edges, as is usual 

 with all the known species of Gorbicula of the Laramie Group; muscu- 

 lar and pallial impressions having the usual characteristics; surface 

 marked with the usual concentric lines. 



Length of one of the largest examples in the collections, 02 millime- 

 ters; height from base to umbo, 54 millimeters; thickness, both valves 

 together, 44 millimeters. 



This fine large species ? the largest yet known in K orth America, has 

 been found only in the Laramie strata east of the Kocky Mountains in 

 Colorado. It is named in honor of Capt. E. L. Berthoud, the first dis 

 coverer of the rich shell deposits of the Laramie Croup in that region. 



Corbicula augheyi (sp. nov.), Plate 21, figs. 4, 5, and 6. — Shell moder- 

 ately large, sub-tetrahedral in marginal outline, postero-dorsal region 

 not flattened, as in C. berthoudi; umbones full, rounded, considerably 

 elevated above the hinge-line, front regularly rounded; basal margin 

 broadly couvex; posterior end truncated, the direction of the truncated 

 margin usually a little backward of a line drawn perpendicularly with 

 the base of the shell; postero-dorsal margin a little convex; hinge well 

 developed; muscular and pallial markings of the usual character; sur- 

 face marked by the usual concentric lines of growth, and usually by 

 very faint umbonal ridges extending from the umbo to the postero- 

 dorsal and postero -basal margins respectively upon each valve. 



Length of an adult example, 46 millimeters; height from base to um- 

 bones, 38 millimeters; thickness, both valves together, 30 millimeters. 



This species has yet been found only in the valley of South Platte 

 Eiver, in Northern Colorado, east of the Kocky Mountains. It is named 

 in honor of Prof. Samuel Aughey, of Nebraska State University, who 

 assisted me in the collection of the type specimens. 



Corbicula umbonella* Meek ; Plate 21, Figs. 7, 8, 9, and 10. — Shell 

 resembling G. obesa White, in most respects, but it is proportionally 

 longer, the umbones are fuller and more elevated, and upon the pos- 

 terior portion there are upon each valve two or three indistinct radiat- 

 ing ruga?. Upon other parts the surface is more than usually smooth. 



"See Bull. TJ. S. Geol. Sur. Terr., Sec. Ser., No. 1, p. 44, where this species is named 

 but not described. 



