CENOZOIC ERA. AGE OF MAMMALS. 393 



Quaternary in the Western Part of the Continent. 



On the Pacific slope the signs of all these movements 

 are clear ; especially are the signs of extensive glaciation 

 magnificent. We shall again vary our mode of presenta- 

 tion by tracing^he condition of things throughout the 

 Quaternary in seas, glaciers, lakes, and rivers. We take 

 seas first, because by this we establish the oscillations. 



Seas. A more elevated condition of land than now 

 exists is plainly shown, not only by the boldness of the 

 Western coast and the existence of a line of bold, rocky 

 islands a little way off shore, a recognized sign of a sunken 

 coast, but also by the remarkable fact that remains of the 

 Quaternary mammoth have been found on one of these 

 islands the Santa Rosa. When this elephant lived, the 

 island was evidently connected with the mainland. 



A subsequent subsided condition is demonstrated by 

 sea-margins in many places. We shall describe briefly 

 the condition of the sea. At that time the Bay of San 

 Francisco was enormously enlarged ; for its waters covered 

 the whole of the flat lands about the bay, including the 

 Santa Clara, Napa, and Sonoma Valleys, and then., passing 

 through the Straits of Carquinas, spread all over the great 

 interior valley of California (Sacramento and San Joaquin), 

 forming an inland sea fifty miles wide and three hundred 

 miles long. The old beach-marks may be traced in many 

 places. Lake Tulare is a remnant of this great inland 

 sea. In Oregon the sea went up the Columbia Eiver, 

 and spread over the Willamette Valley, forming a great 

 sound. From this subsided condition the land rose 

 again, making successive terraces down to the present 

 level. 



Glaciers. It is still doubtful if the general ice-sheet 

 extended on this coast as far south as California, although 

 abundant evidences are found in British Columbia ; but it 



