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Show 422 DR. A. M A C A L I S T E R O N G Y R O P U S 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 in the male. These processes are frequently noticed among such A\noplura as are parasitic upon bristly animals ; thus Heematopinus eurysternus of the O x 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. dicotylis. 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, transverselv 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 the 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 Heematopinus 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 numerous 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 pair. 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 narrow 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 infesting 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 antennae bent and dilated ; no transverse depressed line on prothorax, 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. |