in the British Museum. 127 



Remarks. — This species, wliich seems to bo related to 

 Ch. Javanus, Tlior., is especially remarkable for the i)r.)- 

 nomieed sexual dilfereuce in the structure of the pal()s. 

 In spite of these differences, I have referred the males and 

 the females to the same species on account of the great 

 number in which they occur together, and the similarity 

 in the rest of their structure. 



Ideoroncus mexicanus, Bks. (PI. IX. figs. 2 a-d, 

 PI. X. figs. 1 a-f.) 



1898. N. Bank?, (14) p. 289. 



Cephalothorax (fig. 2 a). — Two well-developed eyes, placed 

 at the lateral margin, and as far removed from the front 

 margin as length of their diameter. The cephalothorax, 

 Avhicli is distinctly longer than broad posteriorly, has parallel 

 sides and is of almost equal breadth behind the eyes, but 

 much narrower in front of them. Anterior margin is 

 marked off from posterior part of head by a line ; it is 

 prolonged into a blunt " epistoma'^ and bordered with a thin 

 membrane. The skin is smooth and provided with mode- 

 rately long, pointed, simple hairs. 



Ahdoriieri. — The abdomen is distinctly longer than broad 

 in the middle, where it is broadest, very narrow' anteriorly, 

 and thereafter almost oval with regularly curved sides. The 

 tergal sclerites are in tliis specimen, which is dilated -with 

 eggs, much shorter than the thinly chitinized membranes 

 between. The sclerites, especially of the anterior and pos- 

 terior tergites, are indistinctly marked off, and the hindmost 

 row of hairs is placed behind their posterior margin. There 

 is a shallow longitudinal depression through the middle of 

 each sclerite; the tergites seem to be smooth. Each tergite 

 bears about four pairs of hairs, -which are longer on the 

 posterior tergites than on the anterior ones ; the tenth and 

 eleventh tergites each bear, in addition to these, two pairs 

 of '^ tactile ^^ hairs. 



The sternites are scarcely different from the tergites, with 

 the exception of the third and fourth, which are very narrow, 

 indistinct, and divided in the middle. 



The sides have well-marked grooves between the segments 

 and possess densely placed, narrow, parallel and longitudinal 

 ridges. 



Antennee (PI. IX. figs. 2 6-^/).— The fingers gape slightly 

 when closed (fig. 2d). The flayellum is composed of three 

 short hairs, which are placed rather apart from each other 

 and provided with some few tiny spines (fig. 2^). The tij) 



