PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 95 



larly ronndecl; basal margin broadly rounded; postero-basal margin ab- 

 ruptly rounded uj) to the postero-dorsal margin, whicli latter margin 

 slopes oblifpiely downward with a gentle convexity from between the 

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

 pecially being long and large and crenulated upon their edges as is usual 

 with all the known species of Corhicula 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, 62 millime- 

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

 together, 44 millimeters. 



This fine large species, the largest yet known in IsTorth America, has 

 been found only in the Laramie ^strata east of the Eocky 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 Group in that region. 

 (Museum No. 11556.) 



Position and locality. — Laramie Group; valley of South Platte Eiver; 

 Northeastern Colorado. 



Corbicula augheyi (sp. nov.), Plate IV, figs. 4, 5, and 6. 



Shell moderately large, subtetrahedral in marginal outline, postero- 

 dorsal region not flattened, as in 0. herthondi; umbones full, rounded, 

 considerably elevated above the hinge line, front regularly rounded; 

 basal margin broadly convex; posterior end truncnted, the direction of 

 the truncated margin usually a little backward of a line drawn perpen- 

 dicularly with the base of the shell; postero dorsal margin a little con- 

 vex; hinge well developed; muscular and pallial markings of the usual 

 character; surface marked by the usual concentric line of growth, and 

 usually by very faint umboual ridges extending from the umbo to the 

 postero-dorsal and postero basal margins respectively. 



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 foun"" only in the valley of South Platte 

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

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

 assisted me in the collection of the type specimens. (^Museum No. 

 11557.) 



Position and locality. — Laramie Group; valley of South Platte Eiver; 

 Northeastern Colorado; associated with the preceding. 



Genus NERITINA Lamarck. 

 Neritina bruneri (sp. nov.), Plate IV, figs. 7 anil 8. 



Shell subglobose; volutions about four; spire much depressed; suture 

 moderately distinct; inner lip broad, its inner edge a little irregular. 

 Surface of adult examples marked by numerous raised revolving lines, 

 which are crossed by strong, dark, zigzag color-markings. Upon young 



