UNDOUBTED TERTIARY SPECIES. 191 



Locality and position. — Ham's I'ork, near Fort Bridger, Bridger beds 

 of the Wyoming Territory ; collections of Colonel Simpson's expedition, in 

 Museum of the Smithsonian Institution ; Tertiary. Dr. Hayden's party 

 have also brought this shell from the same region. 



Genus LIMN^A, Lamarck. 



LlMN^A (LiMNOPHYSA) VETUSTA, Meek. 

 Plate 17, figs. 4, 4 a, and 4 b. 



Limncea vetusta, Meek (1860), Proceed. Acad. Nat. Sci. Philad., XIII, 314; and (1876) 

 in Col. Simpson's Report Expl. acro!?s the Great Basin of Utah, 365, pi. v, 

 figs. 3 a, b. 



Shell small, elongate-subovate, or subfusiform; spire moderately prom- 

 inent, conical, scarcely as long as the aperture; volutions five and a half to 

 six, compressed-convex; last one not very ventricose, sometimes almost sub- 

 cylindrical; suture well defined, with comparatively little obliquity; surface 

 showing only obscure lines of growth; aperture very narrow, subovate; 

 columella with a moderately distinct fold. 



Length, 0.56 inch; breadth, 0.26 inch. 



Among existing species this may be compared with L. decidiosa of Say, 

 some varieties of which it quite nearly resembles. Its body -volution, how- 

 ever, is less ventricose, and its aperture less expanded, than we see in any 

 of the several forms that have been supposed to be varieties of that species. 

 It is perhaps more nearly allied to some of the real or supposed varieties 

 of L. humilis, Say ; though not exactly agreeing with any of them. It varies 

 nmch in form. 



Locality and position. — Ham's Fork, near Fort Bridger ; Colonel Simp- 

 son's collection, in the Museum of the Smithsonian Institution; Tertiary. 



LiMN^A siMiLis, Meek. 



Plate 17, figs. 3 and 3 a. 



Limncea similis, Meek (1860), Proceed. Acad. Nat. Sci. Philad., XII, 314; and (1876) in 

 Col. Simpson's Report Expl. across the Great Basin of Utah, 365, pi. v, 

 figs. 2 a,b. 



Shell small, narrow-subovate, approaching subfusiform; spire rather 

 prominent, nearly as long as the aperture ; volutions five and a half to six, 

 convex; suture rather deep and oblique; surface showing only fine, obscure 



