MANDIBLES AND MAXILLAd 295 
lobes with finely ciliated edges. Between the lips the hard 
and strong mandibles make their dentate cutting edges 
meet. They have no ‘ palp.’ The left mandible, and rarely 
also the right, has a secondary plate on the inner side. 
The molar tubercle is generally a long and strong process 
at right angles to the body of the mandible, with a denti- 
culate crown; but in one family, the Campylaspide, the 
process is thin and stiliform. Between the cutting edge 
and the molar there is usually a row of spines. It is, 
however, distinctive of one family, the Leuconide, that this 
spine-row is absent, being represented only by a couple of 
sete. The first maxille may be roughly described as con- 
sisting of an inner and outer plate, each tipped with spines, 
and of a backward directed ‘ palp.’ The inner plate is an 
expansion of the first joint, and the outer plate an expan- 
sion of the third, the small second joint between them 
being very little conspicuous. Close to the base of the 
outer plate on its outer side is placed the ‘ palp,’ which 
may be the fourth joint of the endopod turned back to serve 
a particular purpose. It is very movably articulated, and 
ends in one or two long setz. Its function is reasonably 
supposed to be that of clearing the branchial sacs from any 
obstructive particles which might be brought in along with 
the water introduced by the action of the breathing ap- 
paratus. In the genus Paralamprops, however, this ser- 
vice must be dispensed with, for there the ‘ palp’ does not 
exist. 
The second maxilla are analysed by Hansen into four 
joints, of which the second is very large, having a row of 
setve on the inner margin and a small terminal plate tipped 
with sete. The third and fourth joints have also each a 
similar small terminal plate, and to the outer rim of the 
third joint is attached a thin plate with curved margin, 
which is explained to be morphologically a weaker develop- 
ment of the fan as it occurs in the Myside. 
Upon the next pair of appendages, the first maxilli- 
peds, the interest of the Cumacean group is above all con- 
centrated, for these present features that are unique among 
the Crustacea. The endopod or limb-like portion of the 
