[From the Anxals and "Magazine of Natural ITistory 



for April 1866. J 



ON 



THE PLEISTOCENE FOSSILS 



COLLECTED BY Col. E. JEWETT AT Sta. BARBARA, CALIFORNIA! 



WITH 



DESCUIPTIONS OF NEW SPECIES. 



BY 



PHILIP p. CARPENTER, B.A., Ph.D. 



The study of the recent and tertiary mollusks of the west coast 

 of America is pecuharly interesting and instructive, for the fol- 

 lowing reasons. It is the largest unbroken line of coast in the 

 world, extending from 60° N. to 55° S., without any material 

 salience esiept the promontory of Lower California. Being 

 flanked by an almost continuous series of mountain-ranges, the 

 highest in the New World, it might reasonably be supposed that 

 the coast-line had been separated from the Atlantic from remote 

 ages. The almost entire dissimilarity of its faunas from those 

 of the Pacific Islands, from which it is separated by an immense 

 breadth of deep ocean from north to south, marks it out as con- 

 taining the most isolated of all existing groups of species, both in 

 its tropical and its temperate regions. When we go back in time, 

 we are struck by the entire absence of anything like the boreal 

 drift, which has left its ice-scratchings and arctic shells over so 

 large a portion of the remaining temperate regions of the northein 

 hemisphere, and also by the very limited remains of what can 

 fairly be assigned to the Eocene age. The great bulk of the 

 land on the Pacific slope of North America (so far as it is not 

 of volcanic origin) appears to have been deposited during the 

 Miocene epoch. Here and there only are found beds whose 

 fossils agree in the main with those now living in the neigh- 

 bouring seas. To trace the correspondences and differences 

 21 321 



