HANNIBAL: A PLIOCENE FLORA FROM CALIFORNIA 331 
there is a general tilting of the strata toward the middle of each of 
the three valleys. 
The source of the waters which supplied this vast lake, and the 
outlet to the ocean are uncertain. The large proportion of coarse 
material in the southern portion of the San Benito Valley suggests 
that a stream of no small size entered here. It is by no means 
improbable that the vast expanse of water was kept up by the 
run-off of the Great Valley of California, through the precursors 
of the Sacramento and San Joaquin rivers. The lake doubtless 
fluctuated widely and a considerable proportion of the sediments 
about the border may have been deposited under fluvial conditions. 
FAUNA 
Aside from the plant remains, the formation contains a fauna 
consisting almost entirely of aquatic mollusca,’ of which a large 
percentage, six out of ten species, still exist in the waters of northern 
California. 
In the following list the species marked with an asterisk are 
living.® 
* Anodonta cygnea impura Say 
Gonidea angulata Cooperi Arnold 
Sphaerium sp. nov 
* Corneocyclas compressa Prime 
* Planorbis trivolvis Say 
* Physa ‘‘heterostropha Say ”’ 
“ Carinifex’’ Sanctae-clarae Hannibal 
* Paludestrina longinqua Gld. 
“Amnicola” Yatesiana Cooper 
* Valvata ‘‘virens Tryon” 
r. John Hain, of Cook, California, obtained a leg bone of an extinct Pro- 
boscidian from these beds near Tres Pinos. far as the writer is aware no other 
recognizable mammal remains have ee found in ‘he formation. 
® Names in quotation marks are subject to revision in a forthcoming paper on 
the fauna of the Santa Clara formation. Amnicola Yatesiana, which in reality be- 
longs to the allied genus Phyrgulopsis, is confined to these beds. The genus appears 
to be valuable for horizon determination in the later Tertiary fresh-water deposits 
of California. 
