356 CRAYFISHES. 



the distal end of the median rib. Length, 90 nun., length of carapace, 41 mm., 

 width of carapace, 20 mm., width of base of rostrum, 6.5 mm., length of rostrum, 

 9 mm., length of areola, 11.5 mm., breadth of areola, 7 mm., length of antennal 

 scale, 7 mm., greatest breadth of do., 4 mm., length of larger claw, 31 mm., 

 breadth of do., 17.5 mm., length of superior margin of hand, 10 mm., length of 

 dactylus, 19 mm., length of smaller chela, 23 mm., breadth of do., 9 mm., length 

 of dactylus, 16 mm. 



There are four specimens of this species in the U. S. National Museum from 

 the rivulets of MM. Bock and Jones, Lake Nahuel Huapi, on the eastern slope 

 of the Cordilleras in Ai'gentina. The chelipeds are preserved in three of these 

 specimens; in two the larger claw is on the left side, in one it is the right, as in 

 the Paris specimen. 



The tip of the rostrum is setose in this species, and in most cases there are 

 a pair of minute, horny, bead-hke lateral teeth just back of the point of the ros- 

 trum. The rostrum is therefore essentially like that of P. bimaculatus. From 

 the latter the present species differs in having much stouter, shorter-fingered, 

 more heavily tuberculated claws, and a somewhat longer metathorax and nar- 

 rower areola. 



Parastacus ayassizii (= bimaculalus) has been recorded from Lake Nahuel 

 Huapi by Ortmann (Proc. Amer. Philos. Soc, 41, p. 293). The specimens 

 should be examined anew with reference to the possibility of their belonging to 

 the present species, P. spinifrons f 



Specimens from Puerto Montt, Lake Llanquihue, on the opposite slope of 

 the Cordilleras, in Chile, are said by Doflein (Sitzungsber. Akad. Wissensch. 

 Miinchen, 1900, 30, p. 133) to agree wholly with my description of P. agassizii ' 

 (= bimaculatus). 



Parastacus bimaculatus (Philippi). 



Astacus bivincutalus H. A. Philii'PI, Analos Universidad Chile, 1894, 87, p. 37S (Chile). 



Parastacus agassizii Faxon, Proc. U. S. Nat. Mus., Feb. 17, 1898, 20, p. 690, pi. 70, figs. 4, 5 (Tidcidiuaiio, 

 Chile). Doflein, Sitzungsber. Akad. Wissensch. Miinchen, 1900, 30, p. 132 (Puerto Montt, Lago 

 Llanquihue, Chile). Lenz, Zool. .Jahrb., Supp., May 2, 1902, 5, p. 731) (Tunibes, Chile). Porter, 

 Revista Chilena de Hist. Nat., Dec. 31, 1904, 8, p. 258, PI. 9 (Contulino and Chilian, Chile). 



'- The error in the branchial formula of P. agassizii as it appears in my paper in the Proc. U. S. Nat- 

 Mus., 189S, 20, p. 692, has been pointed out by Doflein. This error was due to an unfortunate disloca- 

 tion of the table in printing, as is evident on comparing the table of the branchial arrangement in the 

 genus Parastacus on p. 683. 



