NORTH AMERICAN SPECIES OF THE GENUS ATAX 215 



each sex, measured from preserved specimens, proved to be from 0.75 to 

 0.95 mm. for the females and only about 0.5 or 0.6 mm for the males. 



The form is broadly oval, approaching elliptical, and with both ends 

 evenly rounded. The skin shows a fine, even, parallel striation over the 

 whole body of the female; the striae running transversely, while the 

 epimera show the hexagonal reticulation which is characteristic of the 

 group of species which has been referred to as the intermedins group. In 

 the male the same reticulation is visible over the whole body, but is more 

 pronounced and regular on the epimera. 



Eyes large and rather distant from each other. 



Maxillary shield relatively broad, especially posteriorly, where its 

 thicker portion is evenly rounded, while the thinner and relatively slender 

 ancoral process extends posteriad a short distance and ends in a broad 

 tip, which is produced laterally to an unusual degree, forming recurved 

 hooks. Line of separation between the two plates of which the shield is 

 composed distinct. 



Mandibles quite typical in form, the basal segment rectangular, 

 broader posteriorly, with the dorsal posterior angle rounded, ventral pos- 

 terior angle produced and a shallow mandibular groove on the ventral 

 side. Distal segment moderate, claw rather small and slender, and 

 moderately curved. 



The palpi are as a whole quite slender, being only a little thicker than 

 the first pair of legs, and in many respects are characteristic. The basal 

 segment is not unusual; but 2 is much longer along the dorsal margin than 

 along the ventral, the former being moderately convex, the latter nearly 

 straight. It bears on the outer side and near the dorsal margin thi*ee long 

 slender spines, two close together near the middle, a third toward the 

 distal margin; on the opposite side are two spines near the middle. 3 is 

 nearly straight along the dorsal margin, slightly convex along the ventral, 

 and about half as long and two-thirds as thick as 2; it bears a long, slender 

 spine on the outer side close to the proximal margin, and one on the 

 inner side, close to the distal margin and also to the dorsal surface. 4 is 

 the longest of all, yet only half as thick as 2; its dorsal margin is slightly 

 convex toward the base and nearly straight beyond; its ventral surface is 

 concave proximally, but convex distally where it bears the usual number 

 of papillae, of which the paired ones are characteristic. The outer of the 

 two is short and inconspicuous, the inner very large, prominent and 

 flattened laterally; in the male the latter is longer and slenderer, while the 

 former is also longer. Both bear small hairs. Segment 5 is curved ventrad 

 and is nearly circular in cross-section at the base, but at the tip is com- 

 pressed laterally; it bears the usual terminal claws, which, however, are 

 only moderately large and the whole segment is unlike that in the other 

 species grouped with this. 



Epimera in the female occupying about the anterior half of the ventral 

 surface, in the male nearly the whole of it, leaving only room posteriorly 

 for the genital area. Spaces between the groups also much wider in the 

 female than in the male. In the former the first epimeron is nearly rect- 

 angular, and II irregularly triangular, with the inner end produced and 



