NORTH AMERICAN SPECIES OF THE GENUS ATAX 227 



Epimera covering approximately the anterior half of the ventral 

 surface of the body, the spaces between the two groups on either side 

 comparatively narrow, that between the groups of opposite sides greater, 

 especially in the case of the anterior gi-oups, between the inner ends of 

 which is quite an interval. The spaces are. all wider in the female and in 

 that sex the epimera are relatively a little smaller than in the male. The 

 last epimera are relatively long, being longer than broad, while just ex- 

 ternal to the inner posterior angle the posterior margin bears a spur-like 

 projection which curves outwardly and probably serves as a point of 

 muscle attachment. Ill, broadened externally, and an excavation on the 

 outer margin corresponding to the suture between it and IV. 



Legs rather long and slender, the first considerably stouter than the 

 others; the first pair of the female nearly three-fourths the body length, 

 II seven-eights of that length, III slightly exceeding the length of the 

 body, and- IV nearly a fourth longer. In the male the legs are propor- 

 tionately still longer, all exceeding the length of the body, I by a very lit- 

 tle, IV by over two-thirds. Of the individual segments, 4 exceeds 5 and 

 that 6, except in III, where 5 is longer than 4, and in IV where 5 is still 

 more elongated and 6 greatly lengthened, slightly exceeding 5. The seg- 

 ments gi-adually decrease in thickness from 1 to 6 and the last tapers con- 

 stantly from base to tip. The legs are armed with a considerable number 

 of spines of medium length, which form a continuous row along the 

 ventral sui-face of segments 4 and 5, and also along 6 in the case of IV, 

 the spines in this last case shorter. The distal segment is unusually con- 

 tracted toward the tip, and is not cleft to receive the claws, but these last 

 are partly covered by a thin chitinous plate, which, together with several 

 slender hairs, springs from the dorsal side of the segment behind the 

 claws. The claws are bifid, a small accessory claw being developed on 

 the dorsal side of the primary one very close to the tip, except in the case 

 of the first leg, where the secondary claw is longer and springs from a 

 point one-third the way back from the tip of the other. The claws, as a 

 whole, are rather heavy and strongly curved. 



The genital area is situated about midway between the last epimera 

 and the end of the body, slightly nearer, perhaps, to the latter. It is 

 broadly oval in form and nearly as broad as long. In the male the 

 genital cleft is flanked by two reniform plates, which bear five large 

 acetabula, of which the two anterior are in contact, the second separated 

 by a narrow interval from the third, the three posterior in contact, and 

 the two last situated side by side; several short spines are found along 

 the inner margin of these plates. In the female the five acetabula bear 

 the same relationship to one another but the two plates are not so evident 

 and the acetabula seem to be set into the surface of the body itself, though 

 this is thickened over the whole by a deposition of chitin. At the genital 

 opening, short clefts in this thickened area run toward either side and in 

 the four angles formed by these and the genital cleft itself, are four short, 

 stout, curved spines, while other smaller spines occur here and there, 

 scattered over the space within the row of acetabula and along the mar- 

 gin of the genital cleft. 



