No. 6.] NEW SPECIES OF THE GENUS A TAX BRUZ. 281 



The epimera cover most of the under surface of the body, leav- 

 ing but a narrow space between the second and third, and 

 between those of opposite sides. Legs short and thick, the 

 fourth pair longest and only one fifth longer than the body; 

 those of the female slenderer and relatively even shorter than 

 those of the male. The three distal segments of the fourth 

 leg of the male are peculiarly modified, 

 the fourth being compressed laterally 

 through the distal two fifths of its length, 

 and in this compressed portion a bunch 

 of six very large spines, exceeding in 

 length the fifth segment, in two rows on 

 the anterior surface, and on the posterior 



FIG. 2. A. abnonnipes 



surface about nine moderately stout spines; outer side left palpus, 

 the fifth segment is short, at its base 



narrower than the preceding segment, tapering toward the tip, 

 with two very heavy, curved blunt spines on the extensor sur- 

 face and a row of spines along the flexor side, and with a bunch 

 of fine hairs at the distal end ; the sixth is very slender and 

 rather long. The claws are strongly bent and with an accessory 

 tip on the convex side at a distance from the principal tip 

 equalling one sixth the total length. One half of the sexual 

 area of the male is situated 1 on either face of the groove in the 

 posterior surface, the opening being at its bottom ; the ace- 

 tabula are five, in two groups --two anteriorly, three poste- 

 riorly --on a single plate. In the female this plate is divided, 

 the posterior portion with three acetabula being the larger. 



Of this species over 500 specimens have been collected from 

 a number of species of Unio, at Lake St. Clair and Grand 

 Rapids, Mich., Oshkosh, Wis., Chautauqua and Cheektowaga, 

 N.Y. 



III. A. indistinctits n. sp. 



With the preceding and the following this species forms a 

 group of three closely allied species. Of this form only 

 females have been collected, so that there is an absence of the 

 marked structural peculiarities which the males of the others 

 possess, but differences exist sufficient to separate these from 



