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, 

 Pacific 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: — Idaho: Indian Creek, Washington Co. Washington: 

 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. Oregon: Wallowa Lake, Wallowa Co.; Silver 

 Creek, Harney Co.; Bear River, Medford, Jackson Co., Johnson Creek, 

 Portland, Multnomah Co.; Nehalem River, Tillamvok Co. California: 

 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. S. 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 



