Chapter ITT. 



FAUNA L RELATIONS 



1. Pliocene. 



Tlie fauna of the Deadman Island Pliocene strata is somewhat similar to the 

 fauna which is now living in the waters only a short distance oflfshore from San 

 Pedro. Dredging' has shown this, and has also shown that the sediments now being 

 deposited off San Pedro are similar to those which make the strata of the Deadman 

 Island and Timm's Point Pliocene. The Pliocene strata consist for the most part of 

 rather fine clayey brown sand which has its counterpart in the fine sand and mud 

 now being deposited off shore from San Pedro. The Pliocene fauna, although quite 

 similar to the fauna now living off San Pedro, still has many species which are found 

 living only north of that place. To state it more precisely, 18.5 per cent, of the 

 species found in the Deadman Island Pliocene fauna are found living now only to 

 the north of San Pedro. Many of these northern species are limited in range to the 

 boreal waters north of the Puget Sound district. The occurrence in large 

 numbers in the Deadman Island Pliocene of Pecten caurinu^, Panomya ampla, 

 Thyadra bisedu, Pecten hericeus, Lucina acutilineata, Natica clausa, several species 

 of Trophon, and other boreal and subboreaL forms, leads to the conclusion that the 

 strata in which they occur were deposited in water probably much colder than that 

 which is found offshore from San Pedro at the present time. The species found fossil 

 in the Deadman Island Pliocene, and still living at San Pedro, also offer evidence 

 of the northern climatic conditions during later Pliocene times. Of the species 

 living at San Pedro at the present time, and found fossil in the Pliocene, nearly all 

 are more common toward the north. In fact, San Pedro is the southern limit of the 

 known range of many of the species. Boreal or subboreal conditions so near the 

 shore imply more or less similar climatic conditions on the land, at least near the 

 ocean. This being the case, it is more than probable that during the latter part of 

 the Pliocene epoch the climate was much colder on the coast of Southern California 

 than it is at the present time. 



> During the summer of 1901 dredging was carried on In the waters adjacent to San Pedro, Catalina Island, and San Diego, by a 

 party of zoologists under the supervision of Dr. W. E. Ritter, of the University of California. The information obtained by the party was 

 very important, and tiiat regarding the mollusca was esptrially so to the conchologista and paleontologists of this coast, as it extended the 

 known sontliern range of many species heretofore known only north of San Pedro. To Professor Raymond, who had charge of the mollusca 

 obtained, and to Mrs. Oldroyd, who assisted in the classification of the same, the writer is indebted for much of the information regarding 

 the ofTshore fauna near San Pedro. 



( 9 ) (651 June to, 1903. 



