MONOPLATUS. 



in length nearly equal to that of the femora ; at the immediate base 

 incurved downwards, and gradually more robust towards the apex : 

 when seen obliquely, the surface throughout posteriorly is flattened, 

 and raised on either side into two distinct marginations ; on the outer 

 margin near the apex are several spur-like prominences, giving the ap- 

 pearance of a coarsely-toothed saw ; these projections (seen best when 

 viewed obliquely from behind) are six or seven in number, becoming 

 more distinct and frequent as they approach the base : immediately 

 behind the last (the apical) in the margination, between this and 

 the terminal incurved claw, is a short but abrupt ridge, which 

 is armed with several closely disposed minute teeth ; these are not 

 only much more minute, but also more prominent, and acute, and 

 closely arranged, than the projections in the margination. It is 

 remarkable that this serrated emargination is only apparent in the 

 females-, in the males it is entirely wanting, or else represented 

 merely by a little irregularity of outline. The insertion of the 

 tarsus is at the apex of the tibia ; immediately below the insertion 

 are two incurved teeth, situated at the extreme apex of each of the 

 lateral margins of the tibia : the tarsus (Tab. I. fig. 2h) is short ; the 

 basal joint is dilated, its breadth being greater even than that of the 

 apex of the tibia, slightly carinated medially in its upper surface, 

 and flat (in the females this joint is much narrower and more 

 contracted, though of the same length as in the males) ; the second 

 joint is elongate and narrower than the first, attenuated at the base 

 and slightly tapering towards the apex ; in both sexes this joint is 

 of similar form ; the third joint is shorter and somewhat broader, 

 almost bilobed, and covered with a very fine and thick pubescence ; 

 the terminal joint (which is not so elongate as that of the anterior 

 tarsi) is inflated at its extremity into a globular projection, which 

 entirely covers, from above, the apical claw ; the apical claw is 

 minute, bifid, and armed at its inner surface with an almost obsolete 

 tooth. 



The sexual distinctions of this genus are striking and very in- 

 teresting. I premise, however, that they are sexual (and not spe- 

 cific or generic) from the fact that, although during our collecting in 

 Brazil we never succeeded in taking them in copula, both forms 

 were taken together under the same circumstances, at the same 

 times, and at the same different localities in the Organ Mountains. 

 The antennae in the males are longer, the head slightly smaller ; the 

 eyes are distinctly more prominent and globose ; the body is much 

 more narrow, cylindrical, and less robust ; the legs are comparatively 

 longer and more robust, and the basal joint of the tibiae is very 

 broadly dilated : these are sexual distinctions which we should ex- 



