CRAYFISHES. 359 
tion of the carapace and the areola it agrees rather with A. leniusculus. As 
these two species inhabit the same region it is possible that they interbreed and 
produce hybrids. 
ASTACUS TROWBRIDGII Stimpson. 
Astacus trowbridgii stands midway between A. leniusculus and A. klama- 
thensis. As it varies in one direction towards the former species, as has just been 
shown, so, on the other hand it passes through intermediate forms into the latter 
species. Such intermediate forms I have seen from Wilson Creek, Willapa, 
Pacifie Co., and Littlerock, Thurston Co., Washington; and Sinslow River, 
Mapleton, Lane Co., and Wallowa Lake, Oregon. In dealing with small, imma- 
ture individuals it is often difficult if not impossible to decide whether they 
should be assigned to A. klamathensis or to A. trowbridgii. 
ASTACUS KLAMATHENSIS Stimpson. 
Plate 11, 12. 
Astacus klamathensis has a wide distribution in British Columbia, and in 
the states of Idaho, Washington, Oregon, and northern California, in the vast 
area drained by the Columbia River and its tributaries as well as in the smaller 
streams that empty into the Pacific Ocean on the west side of the Cascade Range 
of mountains. 
New localities;-—Ipano: Indian Creek, Washington Co. WaAsHINGTON: 
Goldendale, Klickitat Co.; Granite Lake, Spokane Co.; Naches River, North 
Yakima, Yakima Co.; Crab Creek, [Douglas Co.?]; Creek near Hemp P. O.; 
Salmon River; Prairie Creek; North River; Willapa River, Holcomb, Nasel 
River, Nasel, Pacific Co. Orrcon: Wallowa Lake, Wallowa Co.; Silver 
Creek, Harney Co.; Bear River, Medford, Jackson Co., Johnson Creek, 
Portland, Multnomah Co.; Nehalem River, Tillamvok Co. CaALtrornta: 
Shasta River, near Montague, Siskiyou Co.; Cottonwood Creek, near Horn- 
brook, Siskiyou Co.; Priceland and Garberville, Humboldt Co. 
In a lot of two dozen or more specimens of this species from Portland, Ore- 
gon, in the U. 8. National Museum, a slight variation from the typical form is 
apparent in the lengthening of the rostrum and antennal scale and the more 
pronounced granulation of the chelae. In these regards they show a slight 
approach towards A. trowbridgii. Many of these individuals have lost their 
