NORTH AMERICAN SPECIES OF THE GENUS AT AX 237 



Mandibles like those of A. arcuata and A. ypsilophorus with the line 

 separating the two portions carried backward on the ventral side toward 

 the base, thus causing the distal to encroach on the basal portion. But 

 here the encroachment is greater than in the other cases and the heavy 

 claw seems actually to spring from the side of the distal end of the basal 

 portion. 



Palpi comparatively stout, segment 4 especially noteworthy in that 

 regard. The basal three segments are moderately thick but 4 is unusually 

 so, being through most of its length nearly as thick as 3, though narrowed 

 somewhat before the papillae on the ventral surface is reached and from 

 that point diminishing rapidly in diameter till at the tip it is only one- 

 half as thick as at the base. This segment is also short, being not twice as 

 long as 3 and its length only a little more than one-fifth greater than its 

 diameter toward its base. The paired papillae are very short while the 

 third at the tip is quite rudimentary. Last segment rather long, strongly 

 curved and blunt. Claws at the tip very small and inconspicuous. 



Epimera resembling closely those of A. arcuata but relatively even 

 smaller. 



Legs also resembling those of A. arcuata in general form but rela- 

 tively heavier and differing in the fact that II is longer than III by about 

 one-tenth. The swollen body of the present species is also longer in pro- 

 portion to the length of the legs and only the last pair exceeds it in the 

 male, while in the female none equal it, IV being a trifle shorter. The 

 proportion between the segments resembles those in A. arcuata, as re- 

 gards the relative length of 4 and 5 and the shortness of 6. The distal 

 segment is relatively stouter, and only slightly arcuate. The claws are 

 characteristic, being short and thick with two hooks, the ventral of which 

 is the heavier and somewhat the longer; it projects ventrally at a right 

 angle to the base of the claw and the dorsal hook after continuing for a 

 short distance in line with the base, also turns ventrad at a right angle. 

 The tip of the segment is expanded and has two flattened leaf-like spines 

 dorsally at the distal end which project beyond the claw. 



Genital area. — Similar to that of A. arcuata in general form but ab- 

 solutely larger and relatively broader; number of acetabula greater, in 

 the male 34 to 35, in the female 40 to 41. In the male they cover most of 

 the lateral plates which are reniform in shape, in the female while they 

 reach the inner margin posteriorly, they leave about one-half the width 

 bare anteriorly; two lying against the outer margin exceed the others in 

 size, as is the case in A. arcuata. The inner margin of each plate is pro- 

 longed into a long, flat pointed spine of which the anterior margin is con- 

 vex, the posterior nearly straight, so that it is shaped something like a 

 beak. Its width at the base is equal to one-fourth the length of the inner 

 margin of the plate and it occupies the second fourth of the margin from 

 the anterior end. The genital plates are thick and the margins veiy 

 heav} r , making a pronounced and quite broad border. 



