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 antenne 
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 maxillz 
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 
N 2 
