ANCEUS. 179 



animals scarcely a twentieth of an inch in length up 

 to nearly their full growth. 



In the young or larval stage, the oral organs are similar 

 in both sexes. In fact the cephalon is much alike in 

 both, being subtriangular ; the eyes lateral, placed at the 

 posterior angle of the cephalon, being somewhat larger 

 in the male than in the female. The superior antennae 

 are shorter than the inferior. The mandibles are an- 

 teriorly produced, and developed into sharp-pointed 

 instruments, with the inner margins acutely serrated, 

 the serrations being directed posteriorly. The maxillse 

 are styliform and sharp ; the inner margin of the first 

 pair is slightly serrated. The maxillipods are four- 

 jointed, and each joint supports a strong styliform spine, 

 and the whole of the oral appendages combine together 

 with a sharp process at the apex of the anterior lip, to 

 form a strong lanceolate organ, with which the animal 

 probably cuts its way through the skin of those fish on 

 which it preys. 



Posterior to these appendages, near the inferior and 

 outer angle, stands, what we consider to be, the homo- 

 logue of one of the pairs of gnathopoda. 



From analogy with Tanais, &c., in which the first 

 segment of the body is fused with the head, we should 

 infer that it is the first segment of the body in Anceus 

 which is fused with the head, whence the pair of appen- 

 dages in question would represent the anterior pair of 

 legs (or first pair of gnathopoda), but in Tanais, &c., 

 the second segment of the body is distinct, and bears 

 a pair of legs, whilst in Anceus there is no trace either of 

 this second segment or second pair of legs, unless We 

 suppose the hind part of the head and the pair of appen- 

 dages in question to be the representatives of such 

 second segment and second pair of legs (in which case 



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