1817.] GENUS ASTACUS. 167 



made of slats or osiers, formed somewhat in the manner 

 of a mouse-trap, baited with garbage, &c. attached to a 

 cord and buoy, and sunk by means of a weight. 



2. A. JBartonii. Rostrum mucronate, concave; tho- 

 rax unarmed; hand short, destitute of spines; fingers 

 moderate. 



A. Bartoniif Latr. Gen. Crust, et Ins. v. 6, p. 240, 

 from Bosc*s Hist, des Crust. 



Inhabits the small streams of fresh water of the United 

 States. 



Cabinet of the Academy. 



JBod?/ and extremities with scattered, very visible 

 punctures, more conspicuous on the hands and fingers; 

 rostrum rather short, attaining the tip of the second joint 

 of the peduncle of the inner antenna, suddenly attenuated 

 into an acute termination, without any appearance of late- 

 ral spines; spines behind the eyes obsolete, no vestige of 

 spines on the thorax; anterior feet ^ third joint with short 

 spines beneath, above unarmed; carpus armed with a strong 

 spine within, near the middle, behind which, near the base, 

 is usually a smaller one, on the disk above is an abbreviated 

 deeply indented groove; hands short, with large punctures, 

 distance from the inner hind angle to the thumb joint, 

 hardly equal to one half the length of the thumb, beneath 

 rounded or without an edge; fingers with large punctures, 

 caudal lamellcv ciliated, first segment of the middle one 

 two spined each side at tip. 



Length from the tip of the rostrum to that of the tail, 

 two inches. 



This species is very common in rivulets and small 

 streams of fresh water, under stones, &c. it is familicirly 



