132 INVERTEBRATE PALEONTOLOGY. [WHITE. 



surface of the volutions on the distal side of the row of tubercles without 

 revolving striae, or having one or two indistinct ones; surface upon the prox- 

 imal side of the row of tubercles marked by numerous elevated, slightly 

 waved, revolving striae, which are more distinct about midway of the space 

 than elsewhere, and are very close together near the columella. Only three 

 or four of these striae appear upon the volutions of the spire, because the 

 remainder are covered by each succeeding volution. Aperture oval or sub- 

 elliptical; outer lip having a broad, shallow notch, the retreating angle of 

 which is opposite the row of tubercles, anterior portion moderately extended 

 and abruptly rounded to the columella. 



Length, about nine and a half centimeters, when entire ; diameter of 

 the last volution, twenty-two millimeters. 



This species is more nearly like a true Melanla of Old World type than 

 any of the so-called Melanians of North America with which I am ac- 

 quainted. 



Position and locality. Tertiary strata ; Crow Creek, Colorado, where 

 it was obtained by Mr. W. Cleburn. 



Genus HYDROBIA Hartmaiin. 



Hydrobia recta (sp. nov.). Shell small, very slender, sides of the spire 

 straight ; volutions convex, apparently twelve or more, increasing regularly 

 and uniformly in size from apex to aperture. Surface marked by the 

 ordinary lines of growth. 



Length of one example in the collection, nine millimeters ; diameter 

 of the last volution of the same, . one and a half millimeters. Other exam- 

 ples indicate a length nearly twice as great as that here given. 



Position and locality. Bitter Creek Group ; Almy coal-mines, near 

 Evanston, Wyoming. 



Hydrolna Utahensis (sp. nov.). Shell rather small, elongate-conical, 

 spire moderately produced, its sides straight or nearly so ; volutions about 

 six, convex ; suture impressed ; aperture ovate, a little longer than wide, its 

 distal extremity slightly angular, its anterior end prominent and rounded. 

 Surface marked by the ordinary lines of growth. 



