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IV. On some Struetural Features and Characters. 
Eyes. No real eyes are present, but all species possess 
what may be called an ocular area on each side of the head, 
and this area is always sharply defined from the surroundings. 
In Brachypauropus it occupies a portion of the lateral margin an 
a small part of the lower side of the head, but nothing of its dor- 
sal surface; seen from above (pl. VI, fig. 3b) this area looks al- 
most as a rather narrow, anteriorly rounded band, fastened on the 
lateral margin. In all other species known to me the area extends 
less or more in the upper surface of the head, and in some spe- 
cies (for instance Pauropus oculatus, pl. V, fig. 5a), each area 
Occupies a very considerable portion of this surface. I have ob- 
served that its dimensions on the dorsal side present excellent spe- 
cific characters, and I have especially made use of the proportion 
between its greatest length ånd the distance between the two areas. 
But wishing to avoid the long and uncomfortable denomination 
»Ocular area" I must call them eyes. 
Antennæ. It is well known that the antennæ consist of a 
four-jointed peduncle and two branches, one of which terminates in 
a long ,flagellum", while the other has two flagella of various length 
and a sessile or stalked ,,globulus". But the antennæ present other 
features which have been partly or totally overlooked. Of the hairs on 
the pedunele two inserted near the anterior margin of the fourth joint 
present specific characters in their relative length and in the length 
of the longest hair in proportion to the pedunele. The branch with 
one flagellum is always inserted on the dorsal side of the last joint, 
while the other branch is attached on its lower side; I name there- 
fore these branches respectively the upper and the lower one, and 
"this nomenclature is practical, being independent of the casual re- 
lative direction of the one branch before the other and of their 
varying relative length. The length of both branches in proportion 
to their breadth is very different and presents good specific cha- 
racters. If the upper branch is very long and slender its length in 
proportion to the breadth varies to a certain degree between adult 
