714 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



Genus ACELLA Haldeman. 



Acella haldemani (sp. nov.). 



Shell very small aud very slender; spire longer than the aperture; 

 volutions about six and very obliquely coiled, slightly convex ; last one 

 not ventricose ; aperture only slightly, if at all, expanded, its outer mar- 

 gin, as shown by the lines of growth, being nearly parallel with the axis 

 of the shell. Surface naarked by numerous lines of growth parallel with 

 the border of the aperture and nearly parallel with the axis of the shell. 

 These, owing to the minute size of the shell, are distinguishable only 

 under a lens of considerable power. 



Length 6 millimeters ; diameter of last volution 1^ millimeters. 



The specific name is given in honor of Prof. S. S. Haldeman, the 

 author of the genus. 



Position and locality. — Laramie Group, Yalley of Bear Eiver, near the 

 confluence of Sulphur Creek, Wyoming. 



Genus PHYSA Draparnaud. 



Physa felix (sp. nov.). 



Shell large; body- volution inflated, shouldered at the distal side, 

 which is somewhat abruptly rounded from the outer side and near the 

 suture, at nearly right angles with the axis of the shell ; spire compara- 

 tively small, and appears to have been only moderately elevated. Sur- 

 face marked by the usual lines of growth, except that of the whole shoul- 

 dered portion from the suture outward, which is marked by numerous 

 small, obliquely triangular j)apillse, which are arranged in oblique rows 

 that coincide nearly with the lines of growth. 



The full length of the body-volution was not less than 38 millimeters. 



Only two fragments of this remarkable Fhysa have been discovered, 

 but the characters shown by them, as recorded above, are sufficient to 

 distinguish it from any other species, and when more perfect examples 

 are found it may show diff'erent generic characters also. 



Position and locality. — Laramie Gi'oup, Crow Creek, Colorado, 10 miles 

 above its confluence with the Platte. 



Genus HELIX Linnseus. 



Helix evanstonensis (sp. nov.). 



Shell small, subglobose, wider than high; spire somewhat prominent, 

 its sides convex, terminating in a moderately acute apex ; volutions 

 about six, convex ; last one a little inflated and regularly rounded from 

 the suture to the center of the base ; suture distinct; umbilicus closed 

 with a callus; base flattened in the middle, scarcely depressed; aperture 

 oblique ; outer lip reflected. Surface marked by numerous very distinct 

 raised lines of growth parallel with the outer lip. 



Height 6^ millimeters ; breadth of last volution 9 millimeters. 



