CALIFORNIA ACADEMY OF SCIENCES. 241 



going back perhaps to the eocene epoch, we may expect the 

 land shells will show something similar. The fresh water 

 fossils, as far as known from the eocene lignitic (cretaceous 

 No. 2 of Gabb), and liter strata, probably both miocene and 

 pliocene, consist of spacies mostly quite distinct from the 

 living, though the later beds show a mixture and a few 

 (supposed quaternary) are chiefly identical with recent 

 forms, as would be expected. This fresh water lignitic de- 

 posit was in part again submerged and covered by marine 

 tertiary beds of great depth. No locality has yet been found 

 in which a series can be determined to extend through two 

 or more epochs, though there can be little doubt that such 

 beds exist on the borders of the vast interior basin forming 

 now the central valley of California. It would be supposed 

 that the extensive pliocene lignite beds near Lincoln and 

 lone, ought to furnish such specimens, but having examined 

 the latter carefully, I could find no trace of shells, and sup- 

 posed that this absence was on account of the salt or brack- 

 ish nature of the water in which they were formed, which 

 would be more marked at Lincoln, nearer the centre of the 

 valley. The lone lignite beds have been elevated at least 

 300 feet since their deposition. Pliocene beds containing 

 extinct fresh water shells exist in Bear Eiver Valley, over 

 3,000 feet higher on the mountains, and they doubtless 

 occur in the beds containing the leaf prints, where also land 

 shells should be found, although not yet reported. 



As to the very fresh looking specimen found imbedded 

 under the zygomatic arch of the celebrated "Pliocene" skull 

 of Calaveras County, Prof. Whitney now admits the shell to 

 be more recent, but thinks that the fragment of skull had 

 been washed from its original burial place in a pliocene 

 stratum, into the place where it was found, and there the 

 living snail crawled into the opening, where it died and was 

 cemented there by the tufaceous deposif going on. Even 

 this admitted "change of base" is damaging to the deter- 

 mination of the pliocene age of the skull, though I am not 



