LYMNvEIDiE OF NORTH AMERICA. 95 



mastus or some allied genus. Dr. White does not mention this species 

 in his list of Laramie mollusks in Bulletin 128, U. S. Geological Survey. 



LOWER EOCENE LYMN./EAS. 



Pleurolimnaea tenuicosta (M. & H.). Plate XVI, figures 9-11. 

 figures 9-11. 



This species occurs in the Fort Union and Wasatch formations 

 of the Lower Eocene Period. See ante, page 92. 



Galba minuscula (White). Plate XVI, figures 16, 17. 



Limncea minuscula White, Proc. U. S. Nat. Mus., Ill, p. 160, 1880. — 

 Miller, Journ. Cin. Soc. N. H., IV, p. 133, 1881; Mes. & Camoz. Geol., p. 275, 

 1881.— White, 3rd An. Rep. U. S. Geol. Surv., p. 445, pi. 29, figs. 24-25, 1882; 

 Bull. U. S. Geol. Surv., no. 128, p. 80, 1895. 



Limncea (Leptolimncea?) minuscula White, Amer. Journ. Sci. & Arts, 3 

 ser., XX, p. 45, 1880; An. Mag. N. H., ser. 5, VI, p. 248, 1880; Bull. U. S. Geol. 

 Surv., no. 34, pp. 11, 22, pi. 11, figs. 10-12, 1886. 



"Shell rather small, moderately attenuate; spire much longer 

 than the aperture ; volutions six or seven, moderately convex, the distal 

 border very narrowly appressed against each preceding coil ; aperture 

 small, elongate, subovate ; columellar fold distinct, but not large. Sur- 

 face marked by distinct lines of growth, but no revolving lines have 

 "been detected. 



"The only two examples of this species that have been discovered 

 are broken, but the full length of the larger one is estimated at 9 milli- 

 meters ; diameter of last volution, 3 millimeters ; length of aperture, 

 zy 2 millimeters" (White). 



Types : Cotypes, no. 8907. Plesiotype, no. 20065, U. S. Nat. Mus. 



Horizon : Wasatch, Lower Eocene Period ; on the confines of 

 the Green River (Bridger) and Wasatch formations. 



Locality : Three miles east of Table Rock Station, Sweetwater 

 County, southern Wyoming; Wales, Utah. 



Remarks : This species is placed* in Leptolimncsa by White, but 

 this disposition seems scarcely correct, as the whorls are not quite 

 cylindrical enough to be typical of the group. It resembles elongate 

 forms of the recent caperata Say and particularly the Pleistocene 

 species anticostiana Dall. Its best disposition would seem to be in the 

 subgenus Galba of the genus Galba. 



MIDDLE EOCENE LYMN^EAS. 



Galba vetusta (Meek). Plate XVI, figures 12, 13. 



Limncea vetusta Meek, Proc. Phil. Acad., p. 314, 1860. — Binney, L. & 

 F. W. Sh. N. A., II, p. 72, 1865.— Conrad, Smith. Check List, p. 9, 1866.— Meek, 

 Simpson's Report, Great Basin, Utah, pp. 367, 373, pi. 5, fig. 3, 1876; Bull. U. S. 

 Geol. & Geog. Surv. Terr., Ill, p. 611, 1877. — White, Amer. Journ. Sci. & Arts, 

 ser. 3, XX, p. 45, 1880.— Miller, Jour. Cin. Soc. N. H., Ill, p. 82, 1880; Mes. 



