NO. 1350. NATURAL HISTORY OF THE ISOPODA— RICHARDSON. l7 



in the male the first pair together with the second forms a compound 

 opereidum, consisting of a small oval plate on either side of a median 

 elongated plate, divided by a central suture and terminating in two 

 pointed lobes. 



In the genus Conilera Leach the first pleopoda are opercular, with 

 l)()th branches hard, 



Pleopoda are wanting in the following Epicarid genera: Argeia 

 Dana, males onl}^; Bopi/rus Latreille, males; Bopyro'ides Stimpson, 

 males; Gy<je Cornalia and Panceri, males; Bojjyrina Kossmann, males; 

 J*seudk>ne Kossmann, males; Dajus Kr03^er, males; Asi?idophryxus 

 8ars, females and males; Notophry.vus Sars, males and females; 

 Bathygyge Hansen, males; Athelges Hesse, males; Branchiophryxus 

 Caullery, males and females; Zonojjliryxus Richardson, males; Stego- 

 />/;/'a/,i"?/.s* Thompson, males; Z^//;/oj9A/'y,i'M6- Richardson, males; Portunl- 

 cejxm Giard and Bonnier, males; Parapenseon Richardson, males; 

 Phryi'us Rathke, males; Plefurocrypta Hesse, males; Ergyne Risso, 

 males; males of the Entoniscida?. The pleopoda are represented by 

 fleshy ridges in the females of Bopyroides Stimpson. 



The pleopoda are rudimentary in the following genera: Dajus 

 Kr0yer, females (except the first pair); Leidya Cornalia and Panceri, 

 males; Bopyrm Latreille, females; Prohopynm Giard and Bonnier, 

 males; 6'a«(?r/(?(^;c»w Giard and Bonnier, males; 6^/<//rt//^/o;?Y^ Kossmann, 

 males. 



In some Bopyrid genera the appendages of the pleon are three- 

 branched, asforexample: Phyllodur us Stimpson, females; StegojjhryxuH 

 Thompson, females; Craiicricepon Giard and Bonnier, females; 

 G7\i2>s!cepon Giard and Bonnier, females, has the appendages of the 

 first four segments three-branched, those of the fifth segment bira- 

 mous; Stegias Richardson, females, has the pleopoda of the first three 

 segments three-branched, those of the last two segments two- 

 branched. 



DlpIophryxKS Richardson, females, has the pleopoda four-branched, 

 eight for each of the four abdominal segments. 



The appendages of the pleon are coarseh" pinnate or fringed in 

 Grapsicepon "■ Giard and Bonnier, Z^ic///^? Cornalia and Panceri, Portu- 

 nicepon^ Giard and Bonnier, and Ergyne Risso. In Crancrictpon"' 

 Giard and Bonnier, the dorsal branch of the pleopoda is tubercular. 



In a number of Epicarid genera the pleopoda are single-branched 

 in the adult female. 



3. INTERNAL ANATOMY. 



In the typical form the alimentarj^ canal is a straight tube, without 

 convolutions. It consists (1) of a short, muscular oesophagus lined 



«The dorsal branch in these genera is not homologous with the epinieral lanielhe 

 of the abdoniiral segnient.s of lone Latreille and Kepon Duvernoy. 



Proc. N. M. vol. xxvii— 08 2 



