6 
The posterior maxilla; are rather small and simple in structure, somewhat 
resembling those in the Isopoda. As in the latter, they carry at the end out¬ 
side, 2 small movable lamella;, which partly overlap each other, and are clothed 
with incurved spines. These lamellae, which have often been described as the 
palp, may more properly represent the modified masticatory lobe, as suggested 
by Dr. Boas. In the genus Campylaspis, however, these lamellae are wholly 
wanting. 
Behind these true oral parts there are 3 pairs of limbs, which, judging 
both from arrangement and function, appear to be subservient to mastication, 
and which accordingly ought to be termed maxillipeds. In this respect the 
Cumacea differ very materially from the Edriophthalmia, in which never more 
than one pair of maxillipeds are found. In the higher Crustacea (Decapoda), 
on the other hand, the number of maxillipeds is normally the same as in the 
Cumacea. 
The 1st pair of these maxillipeds is rather short and stout, exhibiting 
inside the end of the basal joint a short conical lobe, clothed with peculiarly 
modified spines and bristles. To the base of these limbs the remarkable branchial 
apparatus is movable appended, so as to admit of being swung freely within the 
roomy branchial cavities. As shown elsewhere by the present author, this ap¬ 
paratus is composed of the modified epipodite and exopodite, the former occupy¬ 
ing the greater part of the apparatus, and carrying inside it the true gill-elements 
in the form of densely crowded lamellae, or more scattered digitiform sacs. The 
exopodal portions of the apparatus extend straight forwards, and together form 
a funnel-shaped tube, through which the water introduced into the branchial cavities 
is at certain intervals expelled by the oscillatory movements of the epipodal 
portions. They are to some extent connected with the latter at the base, and their 
extremities are closely applied to each other, admitting of being exserted from the tip 
of the pseudorostral projection. In some cases, they terminate in 2 incrusted 
lamellae, which work as a valve by alternately opening and closing the anterior 
aperture leading to the branchial cavities. In other cases, they form together a 
long delicate tube, which admits of being protruded and again withdrawn, and 
which is opened and closed at the tip by its own elasticity. The explanation 
here given has been contested by some recent authors : but after renewed 
careful examination. I must still insist on its correctness. Anything analogous 
to this singular apparatus is only found in the Schizopoda (Lophogastrid* and 
Mysidae) and in the cheliferous Isopoda; but in these it is only the epipodite 
which is peculiarly modified for branchial purposes, and in no case does this 
part carry true gill-elements, as in the Cumacea. 
