388 A HISTORY OF RECENT CRUSTACEA 



CHAPTER XXV 



TIIIBE V. — PHREATOICIDEA 



. Family Phreatoicidce. 



Phreatoicus, Chilton, 1882. The only genus. 



The animal is long, subcylindrical, laterally com- 

 pressed. The seven segments of the perteon 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 latei-al sutures or setose ridges. The eyes are small 

 and lateral or absent. The first antenna are short, the 

 flagellum subterminally thickened and carrying olfactory 

 filaments ; the second antennas 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 importaat respects with 

 those of Asellus, only that in the maxillipeds the fourth 

 joint is strongly produced on the outer side. The first 

 limSs of the pera?on 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 sti'ets, which are 

 curved and semicylindical, and the outer branch both in 

 this and the following pairs is two-jointed. The uropods 



