226 AMERICAN JOURNAL 



very abundant, judging from the number of specimens commu- 

 nicated to me by Mr. Eowell. These differ somewhat in form, 

 but the range of variation does not appear to be so great as 

 that of Ph. heterostropha of the waters of the Atlantic and 

 Middle States. 



7. Physa politissima, Tryon. — t. 23, f. 13. 



Description. — Shell oval, spire very short, with the suture 

 scarcely impressed; surface very smooth, highly polished; aper- 

 ture moderate, ear-shaped; labrum regularly curved, not 

 thickened internally; columella much indented at the insertion, 

 scarcely folded, narrow, white, first vertical, then truncately 

 turning to the right towards the base. 



Dimensions. — Length 11 millimetres, diameter 6 mill. 



Hahitat. — Sacramento, California. Rev. J. Eowell. 



My Cabinet. Cabinet of Mr. Eowell. 



Observations. — This shell resembles more closely the British 

 form which Dr. Turton called Ph. alba, than any other with 

 which I am acquainted. In appearance it is singularly grace- 

 ful and pleasing. Its very smooth, shining surface, unmarked 

 by growth lines, and its indented columella, are the most prom- 

 inent points of distinction from all our other species. Only a 

 few specimens were received from Mr. Eowell ; they were all 

 of the size of the one herein described and figured. 



8. Physa occidentalis, Tryon. — t. 23, f. 8. 



Description. — Shell very like Ph. heterostropha; whorls well 

 rounded; suture impressed; spire moderate, sometimes short; 

 apex acute; texture rather thin, surface crowded with growth 

 lines, polished, amber colored; aperture moderately large, 

 outer lip well rounded, thickened within and tinged with red ; 

 columella white, indented, somewhat folded, sharp edged, 

 curved to the right and forwards into a sort of beak at the 

 base. 



"Animal mouse color, foot very slender, with the margins 

 parallel, then regularly converging. When the animal is in 

 motion, the foot reaches to the apex of the shell." — "W. M. 

 Gabb. 



Dimensions. — Length 18 millimetres, diameter 11 mill. 



Habitat. — San Francisco, Centerville, California. Eev. J. 



Eowell. 

 Fort Colville. Geo. H. Horn, M. D., U. S. A. 

 Fort Tejon, Clear Lake, San Geronimo Creek, Sta Clara 



Co., and Dry Creek, Butte Co., California; Umpqua 



Eiver, and Warner's Valley, 50 miles east of Goose 



Lake Valley, S. Oregon. W. M. Gabb. 



