388 A HISTORY OF RECENT CRUSTACEA 
CHAPTER XXV 
TRIBE V.—PHREATOICIDEA 
Family Phreatoicide. 
Phreatoicus, Chilton, 1882. The only genus. 
The animal is long, subcylindrical, laterally coin- 
pressed. The seven segments of the perzeon are distinct, 
with small distinct side-plates. The pleon has six distinct 
segments, the first five laterally produced downwards, the 
fifth longer than any of the preceding four, the sixth 
dorsally fused with the telson, but distinguished from it 
by lateral sutures or setose ridges. ‘The eyes are small 
and lateral or absent. ‘The first antennee are short, the 
flagellum subterminally thickened and carrying olfactory 
filaments; the second antenne have a five-jointed peduncle 
and a flagellum exceeding it in length. The mandibles 
have a dentate cutting edge, accessory plate on the left 
mandible only, a long spine-row, strong molar, and three- 
jointed ‘palp;’ the lower lip is bilobed; these and the 
other mouth-organs agree in all important respects with 
those of Asellus, only that in the maxillipeds the fourth 
joint is strongly produced on the outer side. ‘The first 
limbs of the perzeon are subchelate, of the ‘ gnathopod’ 
form. The rest are ambulatory, the last three pairs facing 
those in front as in most of the Gammaridea. All the 
pleopods have the outer branch ciliated, the inner and 
smaller branchial; the fir-t pair have narrow branches; 
the second have in the male the usual stilets, which are 
curved and semicylindical, and the outer branch both in 
this and the following pairs is two-jointed. The uropods 
a Tee 
wr iatee, TY 
