388 A HISTORY or EECENT CRUSTACEA 



CHAPTER XXV 



TIUBE V. — PHKEATOICIDEA 



F<mdlij Phreatoicidce. 



Phreatoicus, Chilton, 1882. The only genus. 



The animal is long, subcylindrical, laterally com- 

 pressed. The seven segments of the pereeon 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 antennae are short, the 

 flagellum subterminally thickened and carrying olfactory 

 filaments ; the second antennae 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 Asellvs, only that in the maxillipeds the fourth 

 joint is strongly produced on the outer side. The first 

 limbs of the peraeon 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 fin-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 



