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 is to 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, pi. xxxvi, figs. 5, 7. 

 Limncea decisa SAY, Nich. Encycl., ed. 1, 1817. 



Paludina incrassata LEA, Proc. Amer. Phil. S'oc., Vol. II, 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, pi. viii, fig. 3, 

 1834. (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.) 



" 26.00; " 12.50; " " 14.50; " 9.00 " (8858.) Rev d 



" 23.00; " 16.00; " " 13.00; " 9.00 " (8853.) 



" 21.00; " 15.50; " " 12.00; " 8.50 " (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 



