in the British Museum. 131 



Id. mexicanus, Bks. : the minor points in which this species 

 differs from Banks^s description seem not to be sufficient 

 for establishing a new species ; but, on the other hand, we 

 must admit that the description mentioned is too insufficient 

 and lacking in important details for settling the question 

 definitely. 



The differences are the following : — The cephalothorax is 

 only 1*2, not 1"5, longer than broad ; the trochanter of the 

 palps can scarcely be called swollen behind ; the tibia is 

 almost as long as the femur, not one fourth shorter ; the 

 tibia can scarcely be called '' short pedicellate " and is 

 slightly broader than femur, not merely as broad. 



This species is most easily distinguished from Ideoroncus 

 pallidus, Balz. {lo, p. 444), as well as from two undescribed 

 species from Siam, which I have examined, by the flagellum, 

 which consists ol: three short hairs, but especially by the 

 tactile hairs of the hand ; Id. mexicanus bears only a single 

 dorsal one, while the others bear four, placed in a trapezoid. 

 On account of its slender palps and the arrangement of 

 tactile hairs, it presents no similarity to Id. gracilis, Balz. 

 (ii, p. 540). From Id. obscurus, Bks. (i2, p. 66), it differs 

 by the simple undivided galea, by the palps, which are 

 longer than the body, femur of the palps longer than the 

 cephalothorax, and fingers distinctly longer than hand. 



Ideobisium Balzanii, sp. n. (PI. X. figs. 2 a—h.) 



S- Cephalothorax (fig. 2 a). — The comparatively large 

 eyes are placed near to each other at the lateral margin, 

 removed from the front margin a distance about as long 

 as their diameter (fig. 2 a). The cephalothorax, which is 

 a little longer than broad posteriorly, has almost parallel 

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

 slightly narrower in front of them. The front margin 

 passes into a rather broad, rounded, median " epistoma.^' 

 There are no transverse grooves. The skin seems to be 

 smooth, and is provided with moderately long, slender, and 

 pointed hairs everywhere. 



Abdomen. — The abdomen is distinctly longer than broad 

 and broadest in the middle. The sclerites of the tergites 

 are, with the exception of the eleventh, of almost equal 

 breadth and length (the second and third are a little shorter), 

 and well separated from each other by long thin-skinued 

 membranes. The sclerites seem to be smooth and bear 

 some few simple pointed hairs along the hinder margin ; 

 those in the middle are rather short, but the more lateral 



9* 



