262 BRITISH ENTOMOSTRACA. 



eyes of the animal. I^ater authors have proved this 

 opinion to be erroneous, and Pickering and Dana consider 

 them as true sucking-discs, by which the Cahgi attach 

 themselves to the fishes upon which they live. They 

 assert, in proof of the correctness of this opinion, that they 

 have frequently tested the use of these organs by apply- 

 ing the blade of a knife to the inferior surface of the front 

 margin, while the animal was on its back, and that in 

 numerous instances it adhered so firmly to the knife, that 

 it was lifted up and carried to some distance. It exists, 

 however, only in some of the species, and its presence 

 or absence has been used by Nordmann as a generic 

 character. 



The eyes are two in number, and are situated nearly in 

 the centre of the cephalic segment. They are small, 

 simple in structure, of an oval shape, and placed close to 

 each other. In the living animal they are of a red colour, 

 and are slightly projecting. 



The mouth (t. XXXIV, f. 5/) is situated in the median 

 portion of this segment, the eyes being placed directly 

 over part of it. As in the Argulus, this organ consists 

 of a siphon, or conical sucking-tube, composed of two 

 long, slender, styhform organs, curved inwards, and armed 

 on their points with about twelve teeth. These represent 

 the mandibles, and they are inclosed in a sort of sheath, 

 formed from the union of the parts corresponding to the 

 upper and lower lip. Situated upon the sides of the 

 sucking-tube we perceive two pairs of rudimentary ap- 

 pendages (t. XXXIV, f. 5 ^). The one, rising in front of 

 the other, consists of a small basilar joint, terminated by 

 a short, curved apex ; the other is more developed, and 

 is divided into two stout, terminating claws, directed 

 downwards. These constitute the analogues of the two 

 pairs of jaws in the other orders of Crustacea.* 



* Por a fuller exposition of this subject, see the very interesting memoir 

 of M. Edwards upon the Organization of the Mouth of the Siphonostoma, 

 as exemplified by him in the Pa/idarus alatus, in the 'Ann. dcs So. Nat.,' 

 xxviii, 7S. 



