390 A HISTORY OF RECENT CRUSTACEA 
type by having eyes, which are small but distinct, the 
second antennz shorter, the second joint in the limbs of 
the pereeon more dilated, and the pleon furry. In de- 
scribing this species Mr. Chilton mentions that the third 
pleopods have on the outer margin of the basal portion 
‘an ovate appendage which perhaps represents the epipo- 
dite. He finds the males distinguished from the females 
not only by the special organs at the base of the seventh 
pair of limbs, but by rather stronger hands in the first pair, 
and a clasping arrangement in the last two joints of the 
fourth pair. ‘The female appears to have brood-plates on 
the second, third, and fourth segments of the perzeon. 
The figures in Plate XVI. are copied from the papers 
in which Mr. Chilton describes the two notable species 
under discussion. 
While the mouth-organs and pleopods make Phreatoicus 
an unquestionable Isopod genus, the affinity with the 
Amphipoda appears not a little remarkable. The lateral 
compression of the body, the downward lateral production 
of the pleon-segments, the arrangement of the limbs of 
the perzon, the considerable development of the pleon, 
the two-jointed branch in several of the pleopods, the 
strong indication of a distinction between the sixth pleon- 
segment and the telson, and above all the position and 
structure of the uropods, form a group of characters which 
bring this genus nearer to the Amphipoda than any other 
Isopod can claim to be. In the limbs of the pereeon the 
third joint is not very short, as it usually but by no 
means always is in the Gammaridea, nor does the fourth 
joint in the first pair wnderride the fifth as is usual in the 
gnathopods of the Gammaridea. On the other hand the 
clasping arrangement of the fourth pair of limbs is 
strikingly parallel to what is found in the Orchestiide, 
and, as Mr. Chilton points out, the expansion of the 
second joint of the limbs in Phreatoicus australis is similar 
to what is found in so many of the Amphipoda. In his 
admirable discussion of all the characters Mr. Chilton is 
inclined to disallow the Phreatoicide any special proximity 
to the Amphipoda, and is thus induced to remark that 
