2 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.65 



composed of loose washed sand and small drift shells washed high 

 on the beach. Judging from the species that lived here, in the two 

 natural beds mentioned, this place must have been an estuary or flat 

 in a protected place, though exposed to unusually severe storms; 

 a place such as existed at Tims Point 30 or 40 years ago. 



Of the 242 species of shells found in the Nob Hill cut, 115 are 

 found in Puget Sound and north of there. In our four seasons' 

 dredging and shore collecting near Friday Harbor, Wash., we have 

 found a great many of them living. Our dredging has been mostly 

 in the San Juan Channel, where I think more of the Nob Hill fossil 

 species are found living, than anywhere else. The water in the 

 channel is very cold, because the current comes in from the ocean 

 through the Strait of Juan de Fuca. The water in Departure Bay 

 about 75 miles north of there will average 10 degrees warmer the 

 year round, according to Doctor Fraser who is in charge of the Do- 

 minion Marine Biological Station. After the Lower San Pedro time 

 and the climate of California began to get warmer, many of the mol- 

 lusks went north or sought the cold waters of a greater depth. 

 There seems to be a streak of the northern mollusks in about 100 

 fathoms all along the coast as far south as Lower California. It is a 

 fact that there are quite a few southern species' in the lower San 

 Pedro, and also some northern species in the upper; they all lived 

 in the lower San Pedro during that epoch. They did not all go 

 north, some accustomed themselves to the change in temperature, 

 and are found living now near San Pedro. Some withstood the 

 change for a long time and are found in the upper series, but finally 

 died out, and are not now found living here except in very deep 

 water. 



Acknowledgments are due to Dr. Paul Bartsch, of the United 

 i^tates National Museum, and to Dr. W. H. Dall, of the United States 

 (Geological survey, for assistance in the identification of some doubt- 

 ful species and general criticism of the manuscript. I am also deeply 

 indebted to Dr. J. P. Smith, of the Department of Geology in 

 Stanford University, for kindly criticism and much help. Types of 

 the new forms are in the Oldroyd Collection or that of the National 

 Museum. 



LIST OF SHELLS FROM THE LOWER SAN PEDRO PLEISTOCENE 

 SERIES FROM THE NOB HILL CUT, SAN PEDRO, CALIFORNIA. 



Family NUCULIDAE. 



Genus NUCULA Lamarck, 1799. 

 Subgenus Acila H. and A. Adams, 1858. 



>fUCULA CASTRENSIS Hinds, 1843, three small valres. 



Living, Bering Sea-San Diego. 



