NO. I2r6. FOSSIL SHELLS OF THE COLORA DO DESERT— STEARXS. 287 
a proper ligure see the last author's Researches upon the Hydrobmaj/ 
etc. , page 48. 
THE PHYSAS. 
dissociated with Paludedrina and scattered far and wide over the 
desert in immense numbers are various forms of Pkym. Though less 
niunerous than the former, they are particularh' abundant in the 
depressed portion (below sea level) from Indio to Volcano Spring-s, 
their larger size making them far more conspicuous. The desert is 
strewn in like manner with the dead shells of PIanorhl>< ^\\^ Anodonta^ 
far to the south, along the course of New River especially. This dis- 
tribution extends to the " dry lake,'' the before-mentioned Laguna 
Maquata, south of the United States boundary line, where Mr. Orcutt 
observed "" along the bottom of 
the lagoon numerous examples 
of the same species of P/ti/sa, 
l^lanoi'hls^ and Anodonta^^ that 
are found at the north. He also 
mentions the occurrence of cer- 
tain marine shells, Tagelus and 
Cylichna. The first of these, 
as well as a single example of 
Oeinehr'a jpoidsoni Nuttall, were 
collected by me near Indio. 
Regarding the large PJanorhls 
«/><'//'/(9// Gould, Mr. Orcutt found it "about equally abundant '^ * * 
in a fossil state with Physa humerosa.''^ At the stations Avhere 1 col- 
lected both P. amnion and P. gracilentus Gould {\ = P. Jlebmanm 
Dunker) were apparently scarce. So also with Paludedrlna longhiqua 
(= Amnicolalonginqua) Gould. 
The surface of the desert in the neighborhood of these localities and 
for miles beyond those visited by me is covered with the glittering 
fragments of Anodonta calif or niensis Lea, which form a noticeable 
feature of the region, as seen from the moving cars. Perfect valves 
are frequently met with. 
Probably there is no area of equal extent on the face of the earth 
Avhere such an immense number of shells of the genera above named 
may be seen. Millions of the tiny shells of Paludedr'nia^ with their 
varied and beautiful sculpture and the countless thousands of many 
species and varieties of Phym^ indicate this region above all others 
that are known as the metropolis of these groups and prove that the 
environmental conditions throughout this vast territor}' must have 
been preeminently conducive to their multiplication and development. 
While the Pliyms of the desert, as before remarked, are, as a whole, 
rather above the average of their congeners elsewhere in point of size, 
Fig. 6. — Anodonta califoeniensis (Lea), somewhat 
reduced. 
Smithsonian Miscellaneous Collection, No. 201, Aug., 1865. 
