REPORT ON THE LAND AND FRESH-WATER SHELLS COLLECTED IN 

 CALIFORNIA AND NEVADA BY THE DEATH VALLEY EXPEDITION, 

 INCLUDING A FEW ADDITIONAL SPECIES OBTAINED BY DR. C. HART 

 MERRIAM AND ASSISTANTS IN PARTS OF THE SOUTHWESTERN 

 UNITED feTATES. 



By Eobt. E. C. Stearns, Ph. D., 

 Adjunct Curator of the Department of Alollusks, U. S. National Museum. 



The present report treats of the land and fresh-water shells collected 

 in 1S91 by the several subdivisions of the Death Valley Expedition, in 

 southern California and Nevada, between latitude 34° and latitude 

 38° N. The routes followed by several of these 1 parties led them into 

 regions previously unexplored by naturalists, and specimens were se- 

 cured from numerous thermal and mineral springs in the arid deserts 

 of the southern part of the Great Basin, within the Colorado drainage 

 area. The most interesting forms obtained were the two species here- 

 tofore referred to Tryonia, until recently regarded as obsolescent or 

 absolutely extinct, but which were found to be living, as elsewhere re- 

 marked. Helix magdalenensis, another interesting species described 

 from examples collected in the Mexican State of Sonora in 18S9-'90 

 by Mr. Bailey, of Dr. Merriam's Division of Biological Exploration, 

 was detected by Fisher and Nelson several degrees of latitude farther 

 to the north than the habitat of Bailey's original examples and at a 

 very much higher altitude. This latter, by its presence at this north- 

 erly station, contributes to our previous knowledge and data bearing 

 upon the relations between the geographical distribution of species 

 and en vironmental conditions or influences; and two-fresh water forms, 

 not before known, were added to the molluscan fauna of the region 

 traversed by the expedition. 



In additiou to the desert material, small collections were made in the 

 High Sierra and other parts of California, and a few- species are in- 

 cluded from Arizona, New Mexico, and Texas, collected by Dr. 0. Hart 

 Merriam and assistants, while engaged in biological surveys of these 

 regions under the Department of Agriculture. This latter material is 

 important, as illustrating the geographical distribution of the species 



concerned. 



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