293 
is no limit between submentum and mentum, The latter has the 
shape, common among the Culicidæ, and is furnished with 6 sharp 
teeth on each side and one large tooth in the median line. The 
mentum is covered by a fringe of long soft hairs bordering a free 
prominent fold of the skin (fig. 15). 
Beneath the mentum is found the very peculiar organ which 
has been figured by Meinert (1886 PI. I. fig. 5) and better by 
re 
orne 
Manet. 
Fig. 15. Mentum and hypopharynx. 
Raschke (1887 p. 133) but never thoroughly described; it con- 
sists of a tube which is collar-like expanded; probably it has a 
Central pore; it is surrounded by a collar-like part, consisting of 
Plates of chitin, which overlap each other and are furnished with teeth 
along the edges. The organ rests upon a dome-like body supported by 
two lists of chitin and inwardly provided with a thorn-like process. 
Thorns of chitin are also present on the dome-like part. Mein- 
ert's drawing exhibits a circle of hairs rising from the apex of the 
tube; I have not been able to find such hairs; when cut horizon- 
tally the organ (fig. 16) shows a cushion-like layer of cells with 
very large nuclei beneath the dome-like part. Two pairs of diver- 
