FRESII-WATER CRUSTACEA OF THE UNITED STATES. 641 



mm. mm. 



Length of carpus in lirst pair of legs 4.5 4. 7 



Length of hand in first pair of legs 2. 6 52. 0-45, 6 



Length of second pair of legs 22. 10. 5- 9. 6 



Length of merns in second pair of legs 5. 11. 0- 9. 8 



Length of carpus in second pair of legs 4.2 16. 4-13. 6 



Length of hand in second pair of legs 6. 6. 6- 6. 1 



Length of dactylus in second pair of legs 3. 2 10. 5- 9. 6 



The only specimeus which I have seeu vrere obtained by Prof. F. H. 

 Bradley from the Ohio River at Caiinelton, Ind., where he tells me it is 

 takeu for food. 

 Pal^monetes EXIL1PB3 Stimpsou. (Plate I, fig. 1.) 



Annals Lyceum Nat. Hist. New York, vol. x, p. 130, 1871. 



Carapax smooth and the spines of the anterior border slender and acute. 

 Rostrum nearly straight, scarcely reaching the tips of the anteunal 

 scales, and as long as the carapax from the bases of the ocular peduncles 

 to the middle of the posterior margin ; the dorsal crest slightly raised a 

 little behind the bases of the ocular peduncles, and serrated with, seven 

 or eight equidistant, slender, and acute teeth, of which the second is 

 directly above or slightly in front of the bases of the ocular peduncles ; 

 the tip unarmed, slender, and acute ; the inferior edge armed with one 

 or two teeth. Outer flagellum of the antennula much longer than the 

 inner, and its secondary branch, which does not reach the middle of the 

 flagellum, having only the terminal third free. Antennal scale broadest 

 distally and evenly rounded at the tip. 



First pair of legs slender,just reaching to the tips of the antennal scales; 

 carpus a little longer than the merus, slightly thickened distally; hand 

 nearly naked, scarcely thicker than the carpus and only half as long ; 

 lingers as long as the basal portion of the propodus. Second pair of legs 

 slender; carpus nearly twice as long as the merus, slightly thickened 

 distally ; hand slightly thicker than the carpus, and nearly two-thirds as 

 long; fingers slender, nearly naked, and a little shorter than the basal 

 portion of the propodus; third, fourth, and fifth pairs of legs increasing 

 successively in length, the fifth pair reaching to the tip of the rostrum. 



Sixth segment of the abdomen slender, a little longer than the fourth 

 and fifth together. Telson tapering regularly to the extremity, which 

 is quite broad, but terminates in a slender and acute tip, each side of 

 which there is a long and stout spine, and at each lateral angle a shorter 

 one, while between the inner spines there are two long plumose setae, 

 arising from the under side and reaching beyond the tips of the long 

 spines ; each lateral margin armed with two short spines, one near the 

 extremity, and another about three-fourths of the way from the base to 

 tke tip. 



Two specimens, the first from Sandusky Bay, the second from Ecorse, 



Mich., give the following measurements : 



mm. mm. 



Length from tip of rostrum to tip of telson 30. 32. 



Length of carapax from orbit to middle of posterior border 5. 8 6. 5 



S. Mis. 71 41 



