236 CRUSTACEA OF THEJUITEND STATES. [May, 



SPECIES. 

 1. V, Jluviatilis, Rostrum serrated above with about 

 nine teeth, beneath with about two; tail and terminal 

 joints of the abdomen carinated; tail with middle process 

 canaliculate above. 



Astacus fluviatilis Americanus. Seba^ torn, iii. tab. 



n.fig. 2. 



Inhabits North America. 



Rostrum as long as the scales of the antennae, grooved 

 each side, armed above with from seven to nine teeth, of 

 which the posterior one is distant from the others, and two, 

 three, rarely four teeth beneath, which, when but two, are 

 distant and placed nearer the tip; a short spine at the base of 

 each interior antennas, terminating an oblique short cari- 

 na, which is margined above by a groove that is bifurca- 

 ted before its posterior termination, with an acute, short 

 spine in the angle; an abbreviated longitudinal line and 

 groove, sometimes obsolete, originates behind the exterior 

 antennae, forming with the preceding groove the letter N; 

 eyes large; exterior antenna: double the length of the 

 body, scales longer than the second joint of the interior 

 antennae, with a deeply impressed submarginal line; ab- 

 domen with the fourth and fifth segments carinated; sixth 

 segment with the carina more elevated, mucronate behind, 

 a lateral line of longitudinal abbreviated lines on the fifth 

 and sixth segments; tail with the middle process deeply 

 canaliculate and mucronate; feet with the first and second 

 joints of the anterior pair, and second joint of the second 

 pair armed with a spine beneath; fingers with short fasci- 

 cles of spines. Length about eight inches. 



Rarely brought to the Philadelphia market. Seba's 

 figure is without doubt intended for this species, though 



