VOL. III.] Loxvcr Calif ornian Shells. 23 



others have, however, traced the same species so common as fossils 

 in the desert, along New River, and they no doubt exist, sub-fossil 

 if not all living, to the mouth of the Colorado River, or to tide- 

 water, near lat. 32°. 



38. Amnicola longinqua Gould, 1855. Living at Lake 

 Point, Utah, Hemphill. Quaternary, Nevada to Colorado Desert. 



39. Anodonta (nuttaliana) californiensis Lea, 1852. 

 Living, British Columbia to Arizona, Colorado River, y. L. Le- 

 conte, etc. 



40. Gnathodon mendicus Gould, 1851. Living, Colorado 

 estuary. Dr. J. L. Leconte, to Mazatlan, Mexico, in brackish water, 

 Reigen. 



41. Helisoma ammon Gould, 1855. Klamath Lake, Oregon, 

 to Colorado Desert, (and river, J. G. Cooper). 



42. Physa humerosa Gould, 1855. Pyi-amid Lake, Nevada, 

 to Colorado River, and Texas, Blake, Webb, etc. 



43. Planorbis gracilentus Gould, 1855. Colorado Desert, 

 Dr. T. H. Webb. P. leibmanni Dunker, 1844,? from Vera Cruz, 

 Mexico, is supposed by Binney to be the same species, and identified 

 from Texas also. No confirmation of the desert locality recently. 



44. Tryonia clathrata Stimpson, 1865. Colorado Desert, 

 fossil only ? W. P. Blake. Lately reported as living in Utah, 

 (Stearns.) 



45. T. exigua Conrad, 1855. Living, southern Utah (to Dos 

 Palmas Springs, lat. 33° 30', Colorado Desert, Orcntt). 



All the above except 40 and 43, are found in vast nnmbers around 

 the shores of the dry lake constituting the desert, as fossils. Quater- 

 nary, or later. These are chiefly of more northern species than 

 most of the peninsula shells, Nos. 40? and 43 only, being now 

 limited to the south of the boundary, and are all aquatic. Only 41, 

 42, 43 are pulmonate, the others being of orders not represented on 

 the peninsula. 



The portion of the desert south of the boundary is a triangular 

 tract about 70 miles along the boundary,>nd 130 along the 115th 

 meridian (which are nearly at right angles), the third side at foot of 

 the mountains being about 150 miles long, and ending near lat. 

 31*^, thus embracing about 4,550 square miles. A large part of this 



