DRAINAGE OF THE SANTA CLARA VALLEY 9 
it is clear that when the sea came up to the “old shore” line, fish 
could mingle throughout the entire drainage system represented. A 
depression that would place the “later shore” line as indicated 
would cut off the southernmost branch, but would leave the fishes 
free to move through the other branch of the river system. A depres- 
sion bringing the water up to the “present shore”? would separate 
the original single drainage system into five different systems, while 
the faunas would remain more or less the same as the one that occu- 
pied the ramifications of the streams when the drainage all entered 
the sea through a single mouth. It is to be expected that in time the 
faunas diverge, and that the longer they are separated, the greater 
Fic. 2.—Theoretical case to illustrate the effect of coast depression on the fauna of 
streams that originally belonged to one system, but became separated by submergence. 
the difference will be. The Coyote and Pajaro drainages have been 
separated since the streams ceased to be so active, and it seems quite 
reasonable to suppose that that period was at the close of the glacial 
epoch. The ichthyologists state that the fishes in the separate streams 
are already showing perceptible differences—differences that could 
only be expected after a long period of separation. 
Mention should be made of the finding of marine shells in wells 
put dowa on the plain northwest of San José. In the Tenth Annual 
Report of the State Mineralogist of California for 1890, p. 610, Mr. 
Watt says that “marine organisms have also frequently been met 
