APODID^. 
21 
Berthold, to be blood-vessels. Zaddach describes them 
very particularly, and reckons the number to be nine. 
The internal plate or membrane which covers the inner 
surface of the cephalothorax, according to the same author, 
consists of a soft, spongy, cellular substance, and acts the 
part of a branchial plate, or respiratory surface. The 
whole carapace is called by him the “ branchia maxima/’ 
The eyes are two in number; large, compound, situated 
on the upper part of the head, very close to each other, 
of a reniform shape, projecting, and of a bluish-black 
colour. They approach each other much nearer at the 
upper part, leaving a considerable space between them 
interiorly. In this space we see a small elevation, smooth, 
and whitish-coloured, which has been generally described 
as a third eye. It is simple, however, in its structure, 
not compound as the other two are, and thus presents a 
great analogy to the black spot which accompanies the 
eye in the Lynceidse, to be afterwards described. 
When the Apus is laid on its back, and viewed from 
underneath, we see -at the upper part a small portion of 
the carapace extending across, so as to form a plate, the 
surface of which is on a level with the edges of the shell. 
Inserted immediately under the edge of this plate, we see 
the antennae (t. I, f. b , c). These are only one pair, are 
very short, simple, and consist of two small cylindrical 
articulations. Between these antennae is situated the 
mouth (t. I, f. b, a ). This organ is composed, 1st, of a 
superior lip, which is very large, firmly attached to the 
centre of the plate described above, projecting downwards 
so as partially to cover the mouth, and is of a quadri- 
lateral shape (t. I, f. b } b 1) ; 2d, a pair of mandibles 
(t. I, f. b, and f. a ), each consisting of a thick, short, 
curved body, terminated by a flat edge, which is furnished 
with eight or nine strong teeth ; 3d, an inferior lip, con- 
sisting of two lobes and a longitudinal gutter, and which 
Savigny describes as a bifid tongue ; and, 4th, two pairs 
of jaws (t. I, f. a, a 1 , a 2) ; the first pair consisting of two 
parts, the chief of which is a plate ciliated and toothed 
