38 ACARIDEA. 
hairs, but without spines or teeth. The second pair of legs are very thick, the femur 
especially, the latter bearing a strong, straight, slightly denticulated spine on the 
middle of its under surface; the genu and tibia each bear a small tubercle, and 
the tarsus is armed with a broad laminar tooth at some distance from the tip. 
The third pair of legs are comparatively slender, without spurs, except a short one on 
the upperside of the trochanter at the tip. The fourth pair of legs are longer than 
the third, their trochanters bearing two teeth on the upper surface at the apex and a 
short tubercle below; the femora bear underneath a tooth at their base and one at 
their apex; the fourth joint has a blunt tooth and a short spine at its tip. The sternal 
and ventral plates form but one piece of an irregular shape, which protrudes but little 
behind the fourth pair of coxe and ends at some distance from the anal plate; this 
piece has its side-margins excavated for the reception of the coxe, its posterior portion 
being widened laterally and truncate behind; the anal piece is small, triangular; the 
lateral pieces are large and bear the distinctly visible spiracle ; the metapodial piece is 
small, of a triangular or rather oviform shape. The palpi are unarmed, except their 
first joint, which bears a strong spur on the inner side. The labial horns are distinctly 
two-jointed, and have a tongue-like process between them. The chele bear a few 
strongly-marked teeth at their edges; from the centre of the movable branch a long 
process issues, the end of which is rolled up somewhat spirally. 
The female differs from the male in the following characters:—All the legs are 
slender and, with the exception of the apical teeth of the trochanters, do not bear any 
spurs or teeth; the sternal plate is separated from the ventral piece; there are no 
metapodial plates ; and the dimensions of the body are a trifle smaller. 
Two specimens, one male and one female, of this large Gamasid were collected by 
M. A. Sallé at Tuxtla. Their affinity to P. heros, Berlese, from Brazil, is so remark- 
able that I can only treat them as a variety of that species. The Mexican specimen 
(¢ ) before me differs from Berlese’s description in the following characteristics :— 
P. heros, typ. 3 (as described by Berlese). Var. meaicanus, 3. 
Spur of the femur of the second pair thick, curved, Spur of the femur of the second pair straight, denticu- 
with two teeth at the tip; spur of the genu,of late at its margins ; spur of the genu of the second 
the second pair comparatively elevated, dis- pair short, rudimentary, forming only a tubercle ; 
tinctly visible; tarsus of the second pair with- tarsus of the second pair bearing a distinctly visible 
out a tooth at some distance from the apex ; compressed tooth at some distance from the apex ; 
genu of the fourth pair bearing but one tooth genu of the fourth pair bearing two teeth—one 
(not mentioned in the description, but present pointed, spined (like the lateral tooth), and one 
in the drawing). blunt, on the ventral surface of the apex. 
