VRUSTACEANS OF NICKAJACK CA VK—II.\ Y. 431 



or wanting altogether, when present of no detinite shape. First 

 antenna more than half as long as the extended body: willi a small 

 sec'ondar}' flagellum of about two articles; the fiagellum is more than 

 twice as long as the peduncle and composed of about sixteen segments 

 in the male and twenty-nine in the female. Second antenna short, 

 not half as long as the first antenna, flagellum not nuich longer than 

 the second or third segments of the peduncle, composed of fi\'e or six 

 articles. 



First pair of legs of the male with the carpus broad, triangular, and 

 armed with numerous stiff hairs, most of which stand near the inferior 

 angle. Propodus subquadrangular, broadest distally, and pos.si})l\' a 

 little produced at the inferior distal angle; inferior margin with a 

 number of stout hairs; palmar surface with a deep groo\'e, on each 

 side of which are a number of strong teeth and stiff' hairs. Dactyl 

 curved and strong, as long as the palmar surface; in the female these 

 parts differ in being smaller and less strongly armed than in the male. 



Second pair of legs of the male with the carpus similar in general 

 form and armature, but proportionally broader and stouter. Pro- 

 podus considerably larger than that of tirst pair of legs and elongate, 

 twice as long as broad; the greatest width is at a point atiout one- 

 fourth of the distance from the posterior end, and from this point the 

 width of the segment narrows rapidly and nearly uniforndy to the 

 l)aseof the dactyl; the superior margin is slightly convex; the inferior 

 margin, the shape of which has already been descri])ed, is posteriorly 

 provided with a considerable number of long, stout hairs, while the 

 palmar surface, extending over two-thirds of the infero-anterior mar- 

 gin, has a few bristles and ten or more strong teeth in two rows 

 between which the dactyl can be closed; of these teeth the inferior one 

 or two aVe much larger than the others; the dactyl is larger and 

 stronger but less curved than that of the ffrst pair of legs. In the 

 female the second pair of legs is only slightly larger than the tirst 

 pair, and the armature of the propodus is weak. 



The fifth, sixth, and seventh pairs of legs are strongly developed 

 and bear on their posterior 'margins especially an umisual muuber of 

 line, hair-like spines. 



Epimera of the tirst four thoracic segments rather strongly devel- 

 oped, the fourth being unusually large and quadrangular. 



Segments of the abdomen rounded above and without a trace of the 

 spines characteristic of the genus. 



Telson divided nearly to its base, each division truncate, and with 

 three or four rather stout spines. 



Posterior pair of abdominal appendages with the inner rauuis short 

 and rudimentary, the out(M- well developed and (•()m])()se(l of two 

 segments. 



No marked \ariatioa is ohserx able in the alcoholic spcciuuMis. except 



