Thalassinidea and Astacidea. 303 



PanuUrus guttatus, Gray. 



Dr. T. Hale Streets mentions this species among those 

 collected by J. A. McNeil upon the Isthmus of Panama, 

 presumably from the Pacific coast. 



PanuUrus americanusj Lamarck. 

 Also included in the above-mentioned catalogue. 



PanuUrus graciUsy Streets. 



Panrdirus gracilis, Streets, Proc. Acad. Nat. Sci. Phil. 1871, 225, pi. xi. 

 fig. 2. 



This form is described by Streets from a specimen 0*9 inch 

 in length, probably a very young individual. 



Astacus GamheUiy Agassiz. 



This very distinct species appears to be peculiar to the 

 central region of North America ; all the specimens I have 

 seen have been collected east of the Sierra Nevada. 



It is easily distinguished from the species inhabiting the 

 rivers flowing into the Pacific, by the pilose areas upon the 

 upper surface of the chelae, and by the simple rostrum. 



Astacus nigrescenSy Stimpson. 

 Astacus niffrescens, Stimpson, Crust. & Echin. P. S. N. A. p. 52. 



This species appears to be found in most of the larger 

 brooks of the central counties of California, such as the 

 Alameda Creek, Alameda Co., Coyote Creek, Santa-Clara 

 Co., and San-Joaquin Slough. 



It is occasionally sold in the markets of San Francisco. 

 Adult specimens exceed 4 inches in length. 



Astacus Mamathensis, Stimpson. 

 Astacus klatnathensis, Stimpson, op. cit. 64. 



This small species, first found in Klamath Lake by Dr. 

 Newberry, has also been taken in the Columbia River ; and I 

 have collected several individuals in Eel River, Humboldt 

 Co., California. 



Astacus Trowhridgii, Stimpson. 



Astacus Trowbridgii, Stimpson, o;>. cit. 53. 



The terminal spine of the rostrum is less slender than in 

 A. nigrescens ; and a single prominent antero-lateral tooth on 



