Vol. XI] D1CKERSON—PT. REYES AND SANTA ROSA QUADRANGLES 555 



Interpretation of Fauna of the Millerton Formation 



Professor J. Perrin Smith, who examined the fauna col- 

 lected from the beds of the Millerton formation and Tom's 

 Point, recognized that the types in this assemblage were of 

 species considered characteristic of a warm period of the 

 Pleistocene, and he stated that the fauna was equivalent to 

 that obtained from the upper San Pedro beds by Dr. Ralph 

 Arnold. The careful work of Mr. Thomas Oldroyd has in- 

 dicated, according to Professor Smith, that such forms as 

 Chione undatella were restricted to the Upper San Pedro de- 

 posits and did not range downward into the beds of the 

 Lower San Pedro Pleistocene. The writer has prepared a 

 list of the forms obtained from the Millerton beds and has 

 given the present known ranges of these forms in the Recent 

 fauna. None of these species is extinct, but many of the 

 forms, such as Cardium substriatum Conrad, Cardium quad- 

 rigenarium Conrad, Corbula fragilis Hinds, Chione tuidatclla 

 Sowerby, Metis alta Conrad, Semele decisa Conrad, Tagelus 

 calif orniamis (Conrad), Pecten latiauritus Con., Dcntalium 

 neohcxagonnm S. & P., Crepidida onyx Sowerby, and 

 Murex festivus Hinds, are now restricted in range to regions 

 south of Santa Barbara or Monterey. Ranges are given ac- 

 cording to available literature. The other forms in this 

 fauna are species which at present have a great range along 

 the Pacific Coast. From the study of this fauna the writer 

 is led to complete agreement with Professor Smith's corre- 

 lation. With one exception, this is the first time that a 

 fauna of a warm period of the Pleistocene has been reported 

 from San Francisco Bay vicinity. Faunas collected from the 

 Pleistocene terraces around Santa Cruz contain species which 

 are characteristic of that region today. Pleistocene faunas 

 collected by Mr. Bruce Martin from marine terraces on the 

 Oregon Coast also yield Recent species which occur commonly 

 in waters of the ocean at that locality. The Pleistocene 

 fauna of Merced Beach, San Francisco Peninsula, likewise 

 does not suggest any conditions different from those of today. 



Dr. Ralph Arnold 21 in his notable memoir on the marine 

 Pleistocene and Pliocene of San Pedro, California, correlated 



31 Arnold, Ralph, Memoirs of the Calif. Acad, of Sciences, Vol. 3, The Paleon- 

 tology and Stratigraphy of the Marine Pliocene and Pleistocene of San Pedro, Cali- 

 fornia, p. 49, 29-30, 1903. 



