NO. 126b. FOSSIL SHELLS OF THE COLOR A DO DESER T— STEARNS. 273 
circumstances under which the examples from this remote locality 
were discovered. 
The souther! 3' portion of the Great Basin, including the immense 
area from the easterly flanks of the Sierra Nevada across the State of 
Nevada to the westerly flanks of the Rocky Mountain ranges in Utah, 
is characterized by innumerable mountain ranges of varied extent, 
more or less detached or broken; with intervening valleys of a general 
desert aspect; with dry lakes and numerous springs of hot or cold, 
sweet or bitter Avaters, some perennial, others dr}^ or intermittent, 
according to the precipitation of the seasons, which varj- exceedingly 
when one year is compared with another; with an occasional season 
of excessive rainfall, like those of 1840, 1852, 1859, 1861-62, and sub- 
sequently, when every water course and depression was filled to over- 
flowing, and springs that had been dormant for years, their sources 
replenished, became active and continued to flow for months afterwards. 
In considering more particularly the Colorado desert region, we 
find that in these seasons of exceeding precipitation the more depressed 
portion becomes a lake 60 miles long and 30 wide, as in the winter 
months of 1861-62, through the inflow by the way of New River,^ a 
branch of the Colorado which enters the desert from the south, form- 
ing the so-called Salton Sea of more recent years. Aside from these 
unusually rain}' seasons, which are of infrequent occurrence, thunder- 
storms^ of exceeding violence, with a downpour that may be called 
torrential, often occur during the hottest weather; these are usually 
of brief duration and their waters fall upon a comparatively limited 
area. They contribute, however, to the maintenance of animal life 
and help to perpetuate such forms as we are here considering. Atmos- 
pheric agitation at such times, as well as during the hotter weather 
in ordinary seasons, plays its part. Living and dormant individuals 
in and around the springs and pools, as well as the dead shells in their 
immediate neighborhood, are picked up b}- the wind and carried hither 
and thither, the greater part buried under the drifting sands, the spiral 
storms or sand spouts assisting in the general displacement. 
' What is known as "New River" had no existence before the year 1840, when it 
broke away from the Colorado and for a time partly submergecl the desert. For 
several years after a chain of lagoons remained. The same thing has probably 
occurred many times in the history of the desert. H. G. Hanks in Second Report 
of State Mineralogist of California, 1880-1882, appendix, p. 238. 
^Cloud-bursts and waterspouts, accompanied by fearful thunder and lightning, are 
of frequent occurrence. The ground near Frinks Spi-ing and Flowing Wells stations, 
a distance of 17 miles, is cut and gullied in a most remarkable manner. In this dis- 
tance there are no less than 75 bridges and culverts on the railroad track. The 
gullies vary from 5 to 25 feet in depth and about the same in width. The banks are 
so steep and precipitous that, in walking along, one does not see the canyon until it 
yawns at one's feet. These gullies are all caused by the rush of water from cloud- 
bursts and waterspouts. Joseph F. James in Popular Science Monthly, January, 
1882. 
Proc. N. M. vol. x.>civ— 01 18 
