APPENDIX. 



ARTICLE I. 



REPORT OF MR. T. A. CONRAD ON THE FOSSIL SHELLS COLLECTED 

 IN CALIFORNIA BY WM. P. BLAKE, GEOLOGIST OF THE EXPEDITION 

 UNDER THE COMMAND OF LIEUTENANT R. S. WILLIAMSON, UNITED 

 STATES TOPOGRAPHICAL ENGINEERS.* 



PHILADELPHIA, PA., January, 1855. 



SIR : I have examined the very interesting organic remains which 

 you collected in California, and the drawings of such species as were 

 too fragile to preserve, and I herein submit a few remarks upon their 

 geological relations. .There appear to be several distinct groups ; but 

 I cannot pretend, from such scanty materials, to designate what partic- 

 ular formation every group represents. There is no obscurity resting 

 on the deposits of Santa Barbara and San Pedro, which represent a 

 recent formation, in which you inform me the remains of the mammoth 

 occur. The shells are generally those which live in the adjacent 

 waters, and indicate little, if any, change of temperature since their 

 deposition. The littoral character of this formation is very evident. 

 Water- worn shells and fragments show the action of the surf, whilst 

 entire specimens of bivalves, and Pholadidas, and Saxicavae, remain- 

 ing undisturbed in their self-excavated domicils, exhibit the same dis- 

 position of marine shells that is familiar to the observer on all sandy 

 and argillaceous shores. They burrow in clay, mud, or sand, beyond 

 the ordinary action of the surf ; whilst some are scooped out by the 

 tempest-driven surge, and others preyed upon by fishes and marine 

 animals of various kinds, and are thus broken up and deposited 

 among the living species. 



Of the Eocene, and the recent formation alluded to, I can speak 

 with confidence ; but the intermediate beds are of uncertain age. The 

 Ostrea vespertina, Anomia subcostata and Pecten vespertinus, occurring 

 in the bank of Carrizo creek, are unlike any recent forms that I am 

 acquainted with from the Pacific coast, but analagous to Miocene 

 species of Virginia. This formation may, therefore, be regarded as 

 of Miocene origin an opinion in which I am confirmed by some 



* The following reports on the fossil and recent shells were not received in season to be 

 printed in connexion with the author's Preliminary Geological Report. It is deemed best to 

 present these now, even without the plates, as several months will elapse before the draw- 

 ings can be finished and printed for the 4to edition now preparing. 



W. P. BLAKE. 



JULY, 1855. 



