422 DR. A. MACALISTER ON GYROPUS DICOTYLIS. [June 10, 
forms with the unguis about two-thirds of a circle. This tooth is 
capable of being opposed to the claw like a finger and thumb, by 
which means the parasite can ‘ pick his steps” along a hair, although 
uniunguiculate. In one young specimen this tooth appears as a 
knob and not as an incurved spine ; and it is usually a little sharper 
in the female than im the male. These processes are frequently no- 
ticed among such Anoplura as are parasitic upon bristly animals ; thus 
Hematopinus eurysternus of the Ox and H. suis of the Pig both 
possess a similar spur. In these, however, the tooth is at the lower 
end of the tibia, and not removed from it by one-third as in G. dico- 
tylis. The lower end of the femur, the upper end of the tibia, the 
lower end of the latter, and the base of the tarsus are each furnished 
with a small, brown, oval, transversely striated scale on the extensor 
aspect. The tarsus is two-jointed, the unguis faintly transversely 
striated and incurved, ending in a single sharp point. The second 
pair of legs is twice the length of tie first pair, the coxa being short, 
nearly cylindrical, the trochanter bent almost to a right angle with 
the femur and contracted at its coxal articulation. The femur is half 
as long as the entire first limb, slightly curved at its lower end. The 
tibia is also equally elongated and sharply incurved, destitute of a 
tooth at its extremity, this appendage being confined solely to the 
first pair; in this respect it differs strikingly from Hematopinus suis, 
in which a tooth exists on the tibia of each of the three pairs of legs. 
The tibia is garnished with a few scattered hairs, not nearly so nume- 
rous as in G, hispidus or G. gracilis. Unguis curved, triquetrous, 
transversely striated, twice as large as that of the first pair of legs ; its 
extremity split into two teeth, of which the outer is the longer. The 
third pair of limbs resemble the second in every respect ; and both 
exhibit the small brown scales, similar to those described on the first 
alr. 
The abdomen is large, flattened and membranous, composed of ten 
segments, as is usually the case in the genus. Walckenaer, however, 
only found eight in G. gracilis. The first segment is closely united 
to the metathorax, the last is small and nearly hidden. The central 
segments are distinctly separate, margins rather acutely toothed, each 
tooth having a few hairs in its vicinity, not being nearly so pubescent 
as G. gracilis or G. hispidus. The male abdomen is oblong and nar- 
row posteriorly ; the female abdomen is broadly ovate, more sharply 
toothed along its margin, with its segments more distinctly separate ; 
trachea distinct and looped. 
The species of this genus hitherto described have been found in- 
festing Rodents and Edentates, among which may be mentioned the 
Agouti, Guinea-pig,; and Ai. None, as far as 1 know, have been 
found on Pachyderms, with the exception of the present species. 
The characters which I would suggest as diagnostic of this species 
are the following :—Frontal outline convex, non-sinuated ; last joint 
of antennze bent and dilated ; no transverse depressed line on protho- 
rax, which is smaller than head ; brown scales at bases of tibia, femur, 
and tarsus; tibia of fore leg with a prominent spur at its lower third, 
colour ferruginous brown: size } of an inch. 
