136 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



iegata Gray, Turbo fluctuosus Wood, Turritella goniostoma 

 Val, Dendraster excentricus Esch,, Encope micropora A. Ag. 



This fauna is probably lower Quaternary, for while the 

 species are all living, several are not known so far south, 

 some not south of California. This probably shows a slight 

 southward displacement of the isotherm; but the temperature 

 was probably not lowered below 68° F. 



The Quaternary fauna of San Ignacio Lagoon, lat. 27° N., 

 collected by Henry Hemphill, is practically the same as that of 

 Magdalena Bay. This is also true of that of Cerros Island, 

 off Lower California, lat. 28° N., which is now the meeting 

 place of the warm temperate fauna of California ^vith that of 

 the tropical Gulf of California. 



Southern California (San Diego to Santa Barbara, lat. 33°- 

 34° N. ) . The Quaternary of southern California is well known 

 through the work of Ralph Arnold\ under the name of the 

 San Pedro formation. This formation has furnished a rich 

 fauna of beautifully preserved forms, and the study of it has 

 thrown much light upon the Quaternary history of the West 

 Coast. Arnold divides the formation into two divisions : upper 

 San Pedro and lower San Pedro. 



Lower San Pedro. This phase is best developed at San 

 Pedro, near Los Angeles, but is also found at Ventura and 

 Santa Barbara. Important members of the fauna are : Macoma 

 calcarea Gmel., Marcia subdiaphana Carp., Pecten caurinus 

 Gld., Pecten hastatus Sby., Panopea generosa Gld., Phacoides 

 annulatus Rv., Venericardia babarensis Stearns, Amphissa 

 corrugata Hds., Argobuccinum oregonense Redf., Boreo- 

 trophon gracilis Perry, Boreotrophon stuorti Smith, 

 Chrysodomus tabulatus Baird, Natica claiisa B. & S., 

 Tritonofusus rectirostris Carp., Turris perversa Gabb, 

 (all Recent species in the cold water of the Puget Sound 

 region) ; and Pecten jordani Arnold, Crepidula princcps Con., 

 Pisania fortis Carp., extinct species. Of the whole fauna 

 about 90 per cent are living, though mostly not in the southern 

 California waters. The fauna indicates a temperature of about 

 50° F., a displacement southward of the isotherms of 1500 

 miles, and a lowering of temperature of about 12° F., as com- 



1 Paleont. and Stratig. Marine Piocene and Pleistocene of San Pedro, California. 

 <Mem. Calif. Acad. Sci., Vol. 3, 1903. 



