JANIRA. 335 



ISOPODA. ASELL1DM. 



NOKMALIA. 



Genus JANIRA. (Leach.} 

 ONISCODA. (Latreille.) 



Generic character. Pereion serrated along the lateral margins ; 

 pleon having all the segments coalesced into a single plate; 

 covered, in the female, beneath with a large, flat membranous 

 plate concealing the branchial feet ; and furnished at the tip with 

 a pair of elongated bifid uropoda. Outer antennae as long as 

 the animal. Dactyla biunguiculate. 



THIS genus has hitherto been known only by Leach's 

 short and insufficient characters, which have been repro- 

 duced by subsequent authors ; it is closely allied to Jara in 

 its general character, but is at once distinguished by the 

 pair of elongated styles at the extremity of the tail, 

 each of which is terminated by a pair of narrow, slender 

 plates, as in the genus Asellus. 



These styles are liable to be detached at a very slight 

 touch, and hence many specimens of the animal are 

 found destitute of them. They arise in a terminal 

 emargination of the segment, but smaller than in 

 Jam, and having its postero-lateral margin finely ser- 

 rated. In the males, the large terminal segment is 

 furnished at its base, on the underside, with the male 

 organ, which is narrow, flattened, nearly reaching to the 

 extremity of the segment, and with its tip quadriden- 

 tate. In the female, this terminal segment is entirely 

 covered with a very thin membranous operculum, con- 

 cealing the branchial apparatus. The outer antennae, 



