NO. i3r>o. KA TURA L IIISTOR Y OF THE ISOPODA—RICIIA RDSON. 1 5 



iiK'nt only along- the latenil niuroin, and when folded meet in the 

 center. 



The uropoda of the Tylidte and Helleriidw, l)oth families of the 

 tribe Oniscoidea, are also transformed into opercular valves which 

 fold over the terminal segment, below the pleopods, however, while 

 in the Valvifera they inclose the pleopods. 



Many of the Epicarid genera are without appendages to the termi- 

 nal segment of the body, as, for example, Dajm Kroyer, males; 

 xUpldopJiryxus Sars, females only; NotophryxuH Sars, males and 

 females; Zwi(9/>Ary,z'?<« Richardson, males and females; the Crvptonis- 

 cid», females only; the Entoniscid^v, males and females; and the fol- 

 lowing Bopyrid genera, Athelges Hesse, males and females; Pleuro- 

 erypta Hesse, males; Pseudione Kossman, males; Ergyne Risso, males; 

 Argela Dana, males; Bopyriis Latreille, males and females; Prohopyras 

 Giard and Bonnier, males and females; Bopyrlna Kossmann, males 

 and females; Stegopkryxus Thompson, males; Parargela Hansen, 

 males; Munnidion Hansen, males; Branchiophryxus Caullery, males 

 and females; Bathygyge Hansen, males; Bopyroides Stimpson, males 

 and females; Portunicepon Giard and Bonnier, males; Cancrlcepon 

 Giard and Bonnier, males; ^''^r/e Co rnalia and Panceri, males; Pkryxus 

 Rathke, males and females; Parapenseon Richardson, males. 



In a number of the Epicarid genera the uropoda are single branched 

 appendages. This is true of Da jus Kr0yer, females; Plevrocrypta 

 Hesse, females; Pseudione Kossmann, females; Leidya Cornalia and 

 Panceri, males and females; Kepon Duvernoy, females; Grapsicepon 

 Giard and Bonnier, females; Cancricepon Giard and Bonnier, females; 

 Portunicepon Giard and Bonnier, females; Ergyne Risso, females; 

 Glgcmtione Kossmann, males and females; lone Latreille, males and 

 females; x1/y/6'/« Dana, females; /*arar^t/r/ Hansen, females; Cryptione 

 Hansen, males; Enfophilas Richardson, males; Gyge Cornalia and 

 Panceri, females. With this tribe of Isopoda it is the exception for 

 the uropoda to be biramous, although the}^ are double-branched in 

 some genera. 



^. PJeoj)oda. — Respiration is effected ))y means of pleopoda, api)cnd- 

 agcs of the abdominal segments, usually in pairs of live, one pair for 

 each of the first live segments. The pleopoda in general consist on 

 each side of a basal segment carr3ang two lamelhv or rami. In the 

 male the inner lamellre of the second pair bears a slender stylet. 



The first three pairs of pleopoda in the SerolidiB are natatory, the 

 two following pairs branchial; in the Arcturidjv, the two anterior pairs 

 arc natatory, the three posterior pairs exclusivel}' branchial. The 

 ])leopoda are natatory or branchial in the Gnathiida'; they are adapted 

 for both swinuning and respiration in the tribe Flabellifera, with the 

 exception mentioned. In the Asellota and the Epicaridea and for the 

 most part in the Idoteidie the pleopoda are exclusively branchial. 



