8 NOKTH AMERICAN FAUNA [No. 55 



V-shaped canyons coursed by rapid streams. In general features, as 

 well as in plant and animal life, this region is a part of the Trinity 

 or Klamath Mountain system of northwestern California, which also 

 extends northward to include the Rogue River Mountains. 



It is a well-watered region, and except for the higher peaks and 

 ridge tops it is generally well forested. 



The Coast Ranges of western Oregon, lying between the valleys of 

 the Williamette, Umpqua, and upper Rogue Rivers, are largely parts 

 of an elevated and much-dissected plateau, or old coastal plain, 

 deeply eroded into flat-topped ridges with steep, and often terraced, 

 slopes and innumerable deep V-shaped cuts and canyons between. 

 The ridge tops range from 3,000 to about 4,100 feet in height, the 

 highest, Chintimini Mountain, or Marys Peak, just west of Corvallis, 

 being 4,097 feet. Both the Coast Ranges and the coastal plain are 

 largely of sedimentary rocks sandstones, limestones, shales, or more 

 recent alluvial deposits. In places basalt or other igneous rocks 

 crop out on the surface or are exposed in terraces or canyon walls. 



The whole region is well watered. Dense forests and rich under- 

 growth give a well-rounded and smooth appearance and hide most 

 of the details of surface structure. 



The lacustrine and alluvial deposits of the broad valleys of Ore- 

 gon are of special importance and interest because of their rich 

 mellow soils, easily adaptable to profitable agriculture. Most of the 

 larger valleys, such as the plains of the Columbia east of the Cas- 

 cades and the Snake River Valley above the Snake River Canyon, 

 owe their deep soil to the deposits of ancient lake beds long since 

 drained by the lowered river channels. The broad rich valleys of 

 the Willamette, the Upper Umpqua, and the Rogue River may be 

 old lake beds or early embayments of the ocean. Nevertheless, parts 

 of the valley floors are constantly receiving additions of silt from the 

 mountains, spread out by innumerable small streams. Other parts 

 are losing their best soil by erosion. 



The innumerable inland-lake basins of the high plains of eastern 

 Oregon, each with its own type and age of soil and geological depos- 

 its, all lie within the arid area. Generally they are devoted to 

 grazing and ranching, but eventually should include some of the 

 best game lands of the State. 



DRAINAGE 



Drainage is of two distinct types the river and stream drainage 

 to the Pacific Ocean, and the inland-lake or basin drainage of the 

 southeastern part of the State. The river drainage includes the 

 Columbia River system, with its numerous tributaries, and the coastal 

 streams that carry vast quantities of water from the high and humid 

 slopes of the Cascades to the Pacific. 



In the more arid southeastern part of the State are many lake 

 basins of purely inland drainage, really a part of the Great Basin 

 area. Among the larger basins are Malheur, Harney, Alvord, 

 Warner, Abert, and Summer Lakes, all occupying lava-encircled 

 valleys and fed by surface waters or very limited streams from 

 springs. Many extensive playas, or dry mud flats, occupy the bot- 

 tom of other valleys where shallow lakes formed by rains quickly 



