INVERTEBRATE PALEONTOLOGY. [win. 



This species possesses peculiar interest from the fact that it is the first 

 Sucdnea that has been discovered in the Tertiary strata of that great region. 

 Although there are so few salient, specific characters in any species of the 

 genus, this shell , may be readily recognized by its minute spire, the length 

 of which is only a very small part of the full length of the shell, and also 

 by its broadly convex last volution. 



Position and locality. Upper. Green River Group ; Alkali Stage Station, 

 twenty-two miles northwward from Green River Station, Wyoming. 



Genus HELIX Linnaeus. 



Helix riparia (sp. nov.). Shell of medium size, subconical; volutions 

 about five, moderately convex; suture slightly impressed; spire considerably 

 produced for a species of this genus, equal in length to about three-sevenths 

 of the entire length of the shell; proximal side of the last volution broadly 

 and continuously rounded from the outer side; umbilicus small, rather deep; 

 outer lip unknown; aperture oblique, broadly subovate in outline. 



Surface marked by the ordinary distinct lines of growth. 



Position and locality. Lower Green River Group; eight miles below 

 Green River Station, Wyoming. 



* Helix periplieria (sp. nov.). Shell of ordinary size, sublenticular in 

 form; spire low and broadly convex; volutions about five, each broadly 

 convex between the sutures; the last volution abruptly, almost angularly, 

 rounded at the periphery of the shell; under side broadly convex and rounded 

 sharply into a small, deep' umbilicus. Lip apparently not reflexed. 



Surface marked by the ordinary distinct lines of growth. 



Peripheral diameter, about fifteen millimeters. 



Position and locality. Bitter Creek Group; south base of Pine Valley- 

 Mountains, Utah. 



Genus PUPA Lamarck. 



Pupa incolata (sp. nov.). Shell small, turreted, regularly tapering to 

 the apex; volutions about six, convex, regularly increasing in size to the 

 aperture, the last one not being contracted; suture impressed; aperture sub- 

 ovate in outline, its length a little more than one-third that of the whole 

 shell; outer lip thickened, reflexed. 



