OF NORTH AMERICA. 97 



a lens ; aperture subovate, rather narrowly rounded below, and acutely 

 angular above; columella twisted into a moderately prominent fold. 



"Length, 0.39 inch; breadth, 0.19 inch; apical angle slightly con- 

 vex, divergence about 38" (Meek). 



TYPE: U. S. Nat. Mus., nos. 692, 694. 



HORIZON : Bridger formation, Middle Eocene Period. 



LOCALITY: Ham's Fork, north of Fort Bridger, Uinta County, 

 southwestern Wyoming. 



REMARKS : "This variable form is so closely allied to the last that 

 I am nearly satisfied that it is only a variety of the same. Its chief 

 difference consists in having the volutions of its spire a little more 

 convex, and more drawn out, as it were, so as to give decidedly greater 

 obliquity to the suture. It seems to be even more nearly allied to 

 some of the more slender forms regarded by Mr. Binney as varieties 

 of L. humilis of Say; though it is a decidedly more attenuated, less 

 compact shell than that represented by Mr. Binney's figure of L. hu- 

 milis, given on page 63 of his 'Land and Fresh- Water Shells,' published 

 by the Smithsonian Institution. There is scarcely any probability, 

 however, that our shell is identical with any of the existing species" 

 (Meek). 



Meek calls attention to the similarity between this species and 

 vetusta; there is, however, considerable difference, not only in size, 

 but in the general shape of the whorls. Its generic affinities seem to 

 be with Stagnicola. 



There seems to be some discrepancy between the figures of this 

 species in Simpson's Utah report and in the Fortieth Parallel report. 

 The latter agree better with the description, in some respects, than 

 do the former, which fail to show the columella fold and deep sutures 

 mentioned by Meek. The figures from both reports are shown on 

 plate XVI. Figures 18-19 are the same as those used by White in 

 Bulletin 128, U. S. Geol. Surv. (See ante, p. 91.) It is possible that 

 these figures represent a third species. 



OLIGOCENE LYMN^EAS. 



Galba diaphana (Evans & Shumard). Unfigured. 



Lymnea diaphana EVANS & SHUMARD, Proc. Phil. Acad., p. 165, 1854. 

 HAYDEN, Proc. Phil. Acad., p. 158, 1857. 



Limnea diaphana M. & H., Proc. Phil. Acad., 1856, p. 278. 



Limncea diaphana MEEK, Smithsonian Check List, p. 13, 1864. BINNEY, 

 L. & F. W. Sh. N. A., II, p. 72, 1865. WHITE, Bull. U. S. Geol. & Geog. Surv. 

 Terr., Ill, p. 613, 1877. MILLER, Journ. Cin. Soc. N. H., Ill, p. 272, 1880; 

 Mes. & Caenoz. Geol., p. 174, 1881. 



