NO. 1256 FOSSIL SHELLS OF THE COL OR A D DESER T—STEA RNS. 289 
h\ Mr. Vernon Bailey among moss " in an irrigation ditch " at Phoenix, 
Arizona, and by the same party at Magdalena, northwestern Mexico, 
"in a similar situation." It has been reported from other places in 
Mexico, as Avell as from Hot Springs, Lower California, where it was 
detected hy H. and C. R. Orcutt in 1882. 
7'*. lord!, *■■ is rare as a fossil; it does not occur living in the Bonne- 
ville Basin; a few examples have been found on the surface of the 
Sevier Desert." 
For the distribution of the following I quote Dr. Cooper's catalogue. ^ 
"P. gahhu northern California to Lower California. * * * P. 
cmijmllaeea^ Columbia River, latitude 49°, to Owens River, California. 
* * * Physa dia])lianci.^ Lake County, Cal. , to Cape St. Lucas. 
* * * Physa virginea, Oregon and northwestern California to 
Santa Barbara, Cal." 
Call found P. amjmUacea common, living in the Bonneville area; 
it is found also in the Mono Basin, California. P. gabhi was collected 
by Professor Gabb in the Santa Ana River, Los Angeles County; P. 
osculans in Devils River, Arizona (Lloyd), and at Del Rio, Rio Grande 
Valley (Bailey): P. mexicana^ "from Seven Wells, the Colorado 
River, and the Santa Cruz River near Tucson, Ariz., at Laguna, 20 
miles north of Campo, and at Cameron's ranch, San Diego County, 
Cal. Some strongh" shouldered specimens in a subfossil state, from 
the Colorado Desert, are perhaps a variety of this species, which is 
extreme] V variable" (Dall). Professor Dall also identifies a single 
specimen of a physoid form collected bj^Dr. E. A. Mearns in the drift 
of the Santa Cruz River near Tucson, Arizona, as Aple,i'<i hyjjnoriDii.'^ 
Physa virgata^ described from specimens collected by Dr. Webb in 
the Gila River, Arizona; also occurs near San Diego and at Los Angeles, 
where I have collected numerous specimens. 
Physa dlstingxienda^ a species with which I am not familiar, was 
reported by Mr. Orcutt as occurring in a little creek near San Diego 
in 18!t(:). 
Of the 56 figures in Plate XXIII, Nos. 1, 2, and 3 have been made from 
a lot of i92 collected bv Prof. I. C. Russell at Pyramid Lake, Nevada, 
in the extinct Lahontan Lake region. These give a fair idea of the 
differentiation of Physa humerosa from that locality, a species quite 
persistent in its main characteristics, first described from the Colorado 
Desert by Dr. Gould. The other figures represent examples forming 
a second selection from over 1,500 individuals collected by the writer, 
^ Catalogue of AVest North American and many Foreign Shells, etc. Printed for 
the State Mining Bureau, Sacramento, April, 1894. 
^ This extends the distribution of hypnorum by an immense leap to the south, its 
previous most southerly locality considered. It may poi?sibly be shown by additional 
examples to be a long spired variety of ahUa, which is found in Lower California, or 
a slender aspect of niiens, a Mexican species. 
Proc. N. M. vol. xxiv— 01 19 
