ON LAND AND FRESH WATER MOLLUSCA OF 

 LOWER CALIFORNIA. No. 4. 



BY J. G. COOPER. 



A. The Region Expi.ored. 



In the autumn of 1893 Dr. G, Eisen made another 

 collecting trip through that most tropical portion of Lower 

 California lying south of the Tropic of Cancer. Having 

 previously collected chiefly during the dr}' and colder 

 months, it was intended to study the influences of the 

 summer rains and heat on the animal and vegetable life 

 of that region. 



His work was under the auspices of the Academ}- of 

 Sciences, and he was accompanied b}' Mr. and Mrs. 

 Brandegee, as botanists. 



They arrived at San Jose del Cabo September 5th, and 

 were about two months in the field. Unfortunately, the 

 season had been uncommonly dry, and there was only 

 one heavy rain during their sta}', about October 15th. 

 The results of this dr3mess are apparent in the few addi- 

 tions made to land mollusca ; but still there were many 

 interesting observations to record on new local forms from 

 points not before visited, as well as one decidedly new 

 species. 



An aneroid barometer was used to ascertain the approx- 

 imate heights at which the specimens were collected, and 

 gave elevations not far different from those marked down 

 on the U. S. Coast Survey maps of the region. The 

 summits of the peaks, however, were always found to be 

 granitic and waterless, so that few mollusca could exist 

 far above the camping grounds, where springs and alluvial 

 soil caused enough vegetation to supply food and dense 

 shrubby vegetation for the protection of shells from ene- 

 mies or from the hot sun. 



2d Ser., Vol. IV. April 28, 1894. 



