MARINE SHELLS OF LOWER CALIFORNIA. 37 



includes those contributed by ten other persons, who col- 

 lected small numbers from both coasts of the peninsula 

 and the main Mexican shores. 



It thus appears that there are known about 700 to 800 

 species of mollusca from near the entrance of the gulf, 

 and even there very little thorough work in collecting has 

 been done and most of the shells obtained have been 

 dead ones more or less imperfect. 



From small collections hitherto made in the northern 

 end of the gulf, quoted by Carpenter or Stearns, it ap- 

 pears that the species found there are more largely of the 

 temperate fauna, many of them being identical with those 

 from the same latitude on the west coast of the penin- 

 sula. This seems to indicate that the dividing ridge, now 

 3,000 feet or more in altitude, was crossed by one or more 

 channels within geologically recent times. 



The parties collecting for the Academy in 1891-2 were 

 oot well prepared for obtaining marine mollusca, being 

 engaged chiefly in collecting vertebrate animals, insects 

 and plants, on the peninsula and nearest islands, though 

 also preserving such land shells as they met with, when 

 not too busy otherwise. Mr. W. E. Bryant, being often 

 on the seashore in pursuit of vertebrate animals, spent 

 some time in collecting the shells along the beaches, liv- 

 ing or dead, and when La Paz was reached, continued 

 their pursuit onto Espiritu Santo and San Jose islands ly- 

 ing nearly in a line northward from that place, and each 

 about fifteen to twenty miles long. The latter, crossed 

 midway by the 25th parallel of latitude, proved to be the 

 most productive of species of any point visited north of 

 Cape St. Lucas, nearly 150 miles to the south. Besides 

 a large number of beach shells perfect enough for iden- 

 tification, many were obtained in excellent condition 

 through the aid of native divers, who not only dive for 



