On the Geology of the Northwestern Regions of America. 335 
(the Kwichpack of the Russian geographers) lies to the north of 
it The Yukon is a river of great magnitnde, probably the 
largest river in America flowing into the Pacific, not excepting 
the Columbia. For a considerable part of its course it flows to 
the North, but afterwards nearly due west, through a country 
which, as far as can be judged from the descriptive notices of it 
hitherto collected, closely resembles the valley of the Mackenzie, 
With some of the affluents of which it is in fact connected: so 
that here, as in other parts of the Rocky Mountain Chain, the 
Tivers falling into opposite seas interlock at their origin. One or 
more low chains of mountains, formed by the lateral spurs of the 
Rocky Mountains, are prolonged along the Arctic Coast, north of 
the Yukon, .giving origin to several small rivers between the 
month of the Mackenzie and Point Barrow. 
Oregon Territory.—Our acquaintance with the geology of this 
district is very limited, and does not extend beyond the portion 
of country between the Coast Range and the sea, explored by 
the Expedition of Commodore Wilkes. From Mr. Dana's re- 
searches it appears to be occupied chiefly by the tertiary formation, 
which is found at various places from Puget’s Sound to San Fran- 
cisco along the coast-section of Oregon. ‘The rocks of this 
formation are soft sandstones, more or less argillaceous and schist- 
ose, and clay-shales, either firm or crumbling, together with tufa 
and conglomerate. The sandstones and shales have been denuded 
on a vast scale. 
The fossils collected by Mr. Dana were examined by the 
eminent conchologist, Mr. T. Conrad, who assigned them to the 
geological era of the Miocene. They are comprised in the 
following list. 
Mammal. 
1. Vetebre of a Cetacean, 
Fishes. 
1, Vertebre of a species of Shark. 
2, —— ofa Gaaoiew’ alltel to Trigla. 
3. ——, cast of; species not dis' 
Crustacea. 
Callianassa Oregonensis. Balanus. 
Mollusca. at : 
_ Mya abrupta. Pectunculus nitens. 
Thracia trapezoides. Arca daha 
Solemya ventri ; Bt sc ostpae us 
: Vv, a Terebratula nitens. 
ij uncuee Sigaretanscopulosus 
—— brevilineata, Natica saxea. 
ina acutilineata, Bulla pe 
Tellina arctata, Crepidula prerupta; and sp 
