142 
two straight organs. Behind the two median organs and forming 
a square with them there are placed two oblique small organs. 
The structure is not quite alike in the different specimens, as 
the thickness of the chitinous bars and the space between them 
vary. The first median organ which is the most typical, consists 
of a foremost thick chitinous ridge provided with a median longi- 
tudinal fissure, and a hindmost ridge more or less marked. -In the 
hindmost median organ it seems to be the hindmost ridge which is 
provided with a fissure; sometimes there seems to be fissures in 
both ridges. i 
The tibiae, patellae and metatarsi of the legs are sometimes 
provided with deep narrow incisions. 
B. Eyes. The eyes have a very well developed lens and are 
thickly pigmented inwards. 
C. Hairs. The body and especially the legs are provided 
with hairs of different size and structure; the sternum and genital 
plates of the males are mounted with thick, comparatively short 
and pointed hairs which are well articulated and sometimes provided 
with small pointed branches or spines; about seven hairs of the sternum 
are placed on a little hill on each side in front of the median front 
fissure; behind there are placed a comparatively great number of 
hairs of which sometimes a single one is bipartite (pl. IV. fig. 19). 
The copulatory suckers are provided with hairs which will be de- 
scribed later on (pag. 167). The dorsal surface of the ,,head” (pl. IV 
fig..16) is provided with numerous well articulated, comparatively 
clumsy, short and stalky hairs with-small branches. The whole 
abdomen is hairless with the exception of the anal hill and the 
tenth tergite which bear hairs similar to those of the head but 
somewhat longer and more slender. 
In contrast to the body the legs are provided with many hairs 
of different. kinds; only those which are found in greater number 
will be described here. 
(1). Pointed, slightly curved hairs' are found chiefly at the 
distal joints; those of the tarsi (pl. V fig. 2 & 6) are the longest 
