8 J. C. BRANNER 
ever, the submarine topography is best shown, and at these places 
there is suggested a former elevation of the land amounting to more 
than 3,000 feet. In other cases the depths of the dendritic contours 
are only from 1,200 to 2,000 feet, but in these instances the informa- 
tion regarding the former edge of the land appears to be imperfect. 
The absence of a submarine channel off the Golden Gate is probably 
due tothe fact that the silts from the great valley have completely 
buried and obscured it. 
The separation from the main land of the coast islands, Santa 
Catalina, Santa Rosa, etc., was produced by a recent depression that 
left the tops of mountains or hills in the form of islands. This is 
suggested by the topography of the coast islands, and is borne out 
by the flora and fauna’ of those islands. The finding of the remains 
of the mastodon upon the island of Santa Rosa marks? fairly well 
the period of the former elevation of the coast and of land connec- 
tion between the present coast and those islands—that is, the separa- 
tion took place in Pleistocene times. 
The peculiarity of the fish faunas of certain streams referred to 
lies in the fact that in several cases the faunas show that streams 
which are now clearly separated were formerly connected. In most 
cases the former connection was apparently made possible by an 
elevation of the coast which permitted two or three streams to enter 
the ocean by a single mouth. It is assumed that at such time there 
was a single fauna in the entire river system. The later depression 
has submerged the mouth of the stream, and there are now two or 
three or more separate streams entering the sea through as many 
mouths, in place of a single system entering the ocean through one 
mouth. 
In the theoretical case suggested by the accompanying figure 
t John Van Denburgh, “The Reptiles and Amphibians of the Islands of the 
Pacific Coast of North America,” Proceedings of the California Academy of Sciences, 
3d ser., “ Zodlogy,” Vol. IV, No. 1. The author reports four amphibians, nineteen 
lizards, and six snakes (twenty-nine in all) on the islands, of which fifteen live on the 
mainland. 
2 Joseph Le Conte, “The Flora of the Coast Islands of California, etc.,” American 
Geologist, Vol. I (1888), pp. 76-81; Proceedings of the California Academy of Sciences, 
Vol. V (1873), p. 152; American Journal of Science, 3d ser., Vol. XXXIV (1887), pp. 
457-60. L.G. Yates, American Geologist, January, 1890, pp. 51, 52. 
