14 



the flattened umbilical region into sharp crowded lines visible without a glass. 



Color light horn or yellowish, operculum darker. Opercalum paucispiral, 

 the lines of accretion very distinct and regular. 



Dimensions. — Length 25 mill. Diam. maj. 4. mill., min. 3 mill. Length of 

 apert. 2 mill., breadth IJ mill. 



Ilab. — Clear Lake, California. Rev. J. Rowell. My cabinet and cabinet of 

 Mr. Rowell. 



Observations. — This species cannot be compared with any other hitherto 

 described, being much more depressed, and widely distinct in the form of the 

 umbilical region. 



It may possibly form a species of the genus Somatoffyrus, recently proposed by 

 my friend, Mr. Theo. Gill, for a small Mollusc from Iowa, which I described io 

 the Proceedings of the Academy for September, 1862. 



2. PoMATiorsis BiNNEYi, Tryou, t. 1, f. 10. 



Description. — Shell minute, elongated, consisting of four to five very convex 

 whorls ; apex somewhat obtuse ; aperture ovate or nearly suborbicular, both 

 lips rounded ; umbilicus very small. Color light-horn. 



Dimensions. — Length 3 mill. Diam. 1-6 millini. Length apert. 1-25 mill., 

 breadth 1 mill. 



Hab. — Bolinas, California. Rev. J. Rowell. My cabinet and cabinet of Mr. 

 Rowell. 



Observations. — Seven specimens of this very small and exceedingly fragile 

 species were sent to me ; they exhibit, however, all the stages of growth from 

 the very young to adult form. None of them retained the operculum. 



It is much smaller than any other species of Pomatiopsis, and is not likely to 

 be confounded with any of them. It approaches nearest in form to two Earo- 

 pean species of Bi/thinia, B. acuta and B. viridis : the former, however, has a 

 more lengthened, acute spire, and the latter is a more robust and ventricose 

 shell. 



Amnicola protea, Gould, from Colorado Desert, described in Proc. Bost. Soc. 

 N. Hist. V. 129, Oct., 1855, (read Dec. 20, 1854,) is the same as Melania exigua, 

 Conrad, from same locality. Described in Proc. Acad. Nat. Sci. p. 260, Feb., 

 1855. (Read Feb. 13th, 1855.) The shell belongs to a new genus of the family 

 Amnicolidie. Some small fossil shells sent to me by my friend, Dr. F. B. Meek, 

 appear to belong to the same genus. Of course Mr. Conrad's specific name will 

 take precedence over that of Dr. Gould. 



VALVATID^. 



3. Valvata virens, Try on, t. 1, f. 11. 



Description. — Shell turbiniform, consisting of four well rounded whorls, spire 

 elevated, apex acute, sutures deeply indented ; periphery almost angulaled ; 

 umbilicus very wide ; aperture oval or nearly round, the peristome merely 

 touching the body above. Surface closely striate. Color varying from brilli- 

 ant to dark green. 



Dimensions. — Height 5 mill. Diam. maj. 5 mill., min. 4 mill. Length, 

 apert. 2-5 mill., breadth 2 mill. 



Hab. — Clear Lake, California. Wm. M. Gabb. My cabinet and cabinet of 

 Mr. (xabb. 



Observations. — A number of specimens of this species are before me, most of 

 them being about two- thirds grown. It has no American analogue. 



LIMN^ID^. 



4. LiMNvEA Adelin.e, Tryon, t. 1, f. 12. 



Description. — Shell thin, semi-transparent, body whorl large, wide, eonvex ; 

 Bpire small, consisting of five convex volutions, attenuating rapidly to an acute 

 apex, sutures impressed; inner lip thin, reflected, but not covering the umbili- 



