FISHES OF streams TRIBUTARY TO MONTEREY BAY. 
53 
of the Coyote was at one time turned into the Pajaro, it must have carried its species 
into that basin where, meeting no competitors, they probably multiplied and spread 
with great rapidity. This account may be accepted as an explanation of the presence 
of Sacramento species in the Pajaro Basin. It may also be invoked to explain the 
absence of a complete representation of the Sacramento fauna, as only such species as 
were present in the upper portion of the Coyote would have been introduced into the 
Pajaro. The capture of the upper Coyote does not of itself aecount for the occurrence 
of some or even any of these species in the San Lorenzo or Salinas, the basins of which 
are separated from that of the Pajaro by an apparently impassable barrier of ocean water. 
This difficulty is seemingly surmounted by a further consideration of the geological 
history of the region as pointed out by Dr. Branner in a reference to the work of Prof. 
George Davidson.® In his paper Davidson describes many submerged valleys that 
have been discovered by means of numerous soundings along the coast. After con- 
sidering Monterey Bay and remarking that one would naturally expect the whole 
bay to be oecupied by a lOO-fathom plateau, he continues: 
Nevertheless a remarkable submerged valley * * * runs across this plateau and heads into a 
low-lying country immediately behind the 30 miles of shore line of Monterey Bay. It reaches into the 
middle of this low line of beach near the mouth of the Salinas River, and the 50-fathom line is within 
less than half a mile of the shore. The valley which runs east and west is narrow, and at 7 miles from 
the shore the loo-fathom curves are only 2 miles apart and the depth 350 fathoms where the 50-fathom 
would be normal. It broadens and at ii miles has a depth of 615 fathoms. From its northern edge a 
short, deep valley reaches to the northwest, but the 50-fathom curve of this arm is 5 miles from the shore. 
Attention may now be directed to a map constructed from a Coast and Geodetic 
Survey chart of Monterey Bay, plate xx, where various soundings have been con- 
nected by contour lines, thus outlining the great valley or gorge described by Davidson. 
Such a valley could have been formed only by stream erosion, and its presence plainly 
points to a time when the bed of Monterey Bay was entirely exposed and the shore line 
extended beyond the present 6oo-fathom contour. Dr. Branner believes that the for- 
mation of the alluvial fan by the Coyote was coincident with this period of elevation 
of the coast, which brought about a climate of greater humidity than we now have and a 
correspondingly large amount of stream activity. At this time the Salinas was prob- 
ably the chief river of the system, and flowing down the great valley, received first the 
Pajaro and then the San Lorenzo from the narrow canyons which extended toward the 
northeast. There was then an open waterway between the rivers of the Pajaro sys- 
tem and any species which might chance to be introduced from the Coyote by a shift of its 
headwaters would soon extend its range throughout the system. 
It will now be recalled that of the streams tributary to Monterey Bay, the Pajaro 
alone contains a full representation of the fluvial fauna of the system. The Salinas con- 
tains six species and the San Lorenzo three. The question at once arises, if these streams, 
being of similar character and of about the same volume, were once connected with 
the Pajaro, why do they not now contain all its species ? 
Proceedings California Academy Sciences, 3d ser., Geology, vol. i, p. 73-103. 
