150 A REVISION OF THE: ASTACIDAS. 
In the remaining species of Astacus the first abdominal appendages are 
simply rolled, never bifid nor toothed at the end, neither are there hooks on 
any of the thoracic legs in the male. 
THE NORTH AMERICAN ASTACTI. 
Six species of Astacus have been described from Western North America, 
viz.: — A. Oregunus Randall, 1839; the type of this species was lost, and 
the figure and description are insufficient for its determination ; it is perhaps 
the same as A. leniusculus Dana. A. Gambelii Agassiz, first described as a 
Cambarus in 1852 by Girard; the types of Girard are in the Philadelphia 
Academy. A. /eniusendus Dana, 1852; type in the collection of the Smith- 
sonian Institution, Washington, D. C. A. nigrescens, A. Trowbridgii, and 
A. Klamuathensis, described by Stimpson in 1857; there are types of A. Trow- 
bridgii in the Smithsonian Institution, the Museum of Comparative Zoilogy, 
and the Peabody Museum of Yale College; Dr. Hagen examined types of 
A, nigrescens and A. Klanathensis communicated by Stimpson. 
Distribution. —The nearly related species A. lemusculus and A. Trowbridgu 
are found in the lower part of the Columbia River, Puget Sound, and adja- 
cent regions. To the southward near the coast, in the neighborhood of San 
Francisco, A. wyrescens appears to be the dominant species. It perhaps ex- 
tends northward near the coast as far as Alaska. In the more elevated 
regions of the Northwest, in Oregon, Washington Territory, and British 
Columbia, A. A7lamathensis is found. The most eastern of the American 
Astaci is A. Gambelii, which is found in the Great Salt Lake Valley and in 
the upper waters of the Snake River, Idaho. From this region it has passed 
over the divide into the Yellowstone Valley, and invaded the domain of the 
Cambari as far as the confluence of the Yellowstone and Missouri Rivers. 
An examination of the physical geography of this region shows that the 
migration of a Western species into the Mississippi basin at this point is no 
difficult matter, the divide separating the waters of the Yellowstone from 
those of the Snake River being very low, hardly above the level of the 
ancient Yellowstone Lake.* 
Compared with the European species, the American Astaci have the 
* See W. H. Holmes’s Report on the Geology of the Yellowstone National Park, in Twelfth Ann. Rep. 
U.S. Geolog. and Geograph. Survey of the Territories for 1878, Part II. p. 56, 1883. 
