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 

 inferiorly. 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 LynceidaB, 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. 6, <?). 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. I), 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. 0, a 1 , a 2) ; the first pair consisting of two 

 parts, the chief of which is a plate ciliated and toothed 



