276 



SUCTORIAL CRUSTACEA ; CALIGUS. 



Its body is composed of two principal portions ; the anterior one 



covered by the oval 

 shield or carapace 

 (Fig. 500, a); the 

 d e posterior, forming the 

 termination of the tho- 

 rax and the rudimen- 

 tary abdomen, is di- 

 vided into rings. The 

 first pair of antennae is 

 reduced to the condi- 

 tion of small flattened 

 plates, in some species 

 bearing a sucker. The 

 antennae of the second 

 pair (b) also are short, 

 and composed of only 

 two joints. At c is 

 seen a sucker, formed 

 by the labrum, and 



FIG. 499,-CALiGus. FIG. SOCK-UNDER SIDE OF CALIGUS. inclosing the mandi- 



bles. The maxillae 



(d, e) are represented by two pairs of rudimentary appendages, 

 situated at the sides of the sucker, one of them terminated by 

 horny claws directed backwards. The feet-jaws (/, g, h), to the 

 number of three pairs, are instruments of prehension, by which the 

 animal attaches itself ; and behind the last pair of these, there is 

 a forked appendage on the central line (i) 9 which probably assists 

 in the same object. There are four pairs of thoracic legs ; of 

 which the first three (j 9 k, I), formed for swimming, are situated 

 beneath the carapace ; whilst the last (m), which comes forth 

 behind it, is rather adapted for walking. The abdomen forms 

 but a single segment ( p ) ; and is furnished with a pair of small 

 fin-like appendages (q). One of the most curious parts in the 

 structure of this animal, is the pair of long tubes (r), which are 

 attached to the sides of the abdomen of the female ; these appear 

 to be receptacles for eggs, and to be analogous to the capsules of 

 the Cyclops, &c. (Fig. 489). 



