THE NATURAL HISTORY SURVEY. 359 
subsolidum. The females are very globose and may easily be 
distinguished from the males, which are comparatively slen- 
der. The interior of the aperture is frequently bluish or pur- 
plish, and the pinkish substance of the shell cannot be made 
out until the shell is examined by transmitted light. An ex- 
cellent method of identifying this species isto scratch the epi- 
dermis from a spot on the shell, when the beautiful pink tint 
will be seen. This seems to be a rather widely distributed 
species and is found in all parts of the territory. Mr. T. Jen- 
sen has a very fine, large, reversed specimen in his collection. 
149. Campeloma decisum Say, pl. xxxvi, figs. 5, 7. 
Limnea decisa SAY, Nich. Encycl., ed. 1, 1817. 
Paludina incrassata LEA, Proc. Amer. Phil. Soc., Vol. IJ, p. 243, 1842. 
Paludina decapitata ANTHONY, Proc. Phil. Acad., p. 71, 1860. 
Melantho melanostoma CURRIER (MSS.?) 
Melantho geniculum CONRAD, N. Fr. W.Sh., U.S., p. 48, pl. viii, fig. 3, 
1854. (Variety.) 
Shell: Elongate-ovate, rather solid, subfusiform; color 
dark green, generally very uniform, but with here and there 
a brown streak representing a former edge of the aperture; 
surface smooth, shining, lines of growth numerous, very fine, 
crowded, crossed by numerous microscopic revolving lines; 
beneath the green epidermis the shell is chalky white, apex 
(when present) very small, rounded, color light horn; spire 
elevated, conic, obtuse near the apex, frequently truncated; 
sutures well impressed; whorls six, rounded, the upper whorls 
of the spire being frequently eroded; aperture elongately- 
ovate, very nearly entire, rounded below and a little contracted 
above, bluish-white within; peristome acute, simple, a dark 
brown band bordering it on the outside; the columellar wall 
of the aperture is covered by a callus which is bordered with 
dark brown and connects the terminations of the peristome; 
the parietal wall and columella form almost a straight line in 
typical (male) specimens; base rounded, made imperforate by 
the reflection of the aperture. 
Lgth., 28.50; width, 17.50; aper.lgth., 15.50; width, 10,00 mill. (10110.) 
“ 96.00: “ 1250; “ “ 414.50; “ 9,00 “ (8858,) Reve ed 
“ 93.00: “ 16.00; “ “ 18,00; “ 9,00 “ (8853.) 
“ 91.00; “ 15.50; “ “ 12.00; “ 850 “ (8856.) 
Animal; Pale or bluish white, covered over thickly with 
salmon-colored spots, under portion of foot pale bluish-white; 
head small, distinct; rostrum small, cylindrical; tentacles 
