THE ISOPODA 219 



Asellota stand somewhat apart from the rest, especially as regards 

 the structure of the pleoi)ods. On the other hand, the Epicaridea 

 are closely related to some of the Flabellifera, the systematic value 

 of the modifications due to parasitism ha\'ing been here as elsewhere 

 somewhat overestimated. The Gnathiidae, again, are an aberrant 

 family whose relation to the more normal Flabellifera is not clear, 

 and the same may perhaps be said of the Authuridae. 



Order Isopoda, Latreille (1817). 

 Sub-Order 1. Asellota, Latreille (1806). 



All the abdominal somites coalesced (except in Stenasellus) ; antennal 

 peduncle of six segments ; mouth-parts never suctorial ; coxopodites of 

 thoracic legs small, the last six pairs freely movable ; first pair of pleopods 

 differing in the two sexes, second pair absent in female ; uropods sub- 

 terminal, often biramous, styliform. 



Family Aselliuae. Asellus, Geoffrey ; Stenasellus, Dollfus. Family 

 Stenetriidae. Stenetrium, Haswell. Family Parasellidae. Jcmira, 

 Leach ; Jacru, Leach ; Mimna, Boeck ; Desmosoma, G. 0. Sars ; Nanno- 

 niscus, G. 0. Sars ; Munnopsia, M. Sars ; Eurycopc, G. 0. Sars ; Acantlw- 

 co-pe, Beddard. 



Sub-Order 2. Phreatoicidea, Stebbing (1893). 



Abdominal somites all free ; antennal peduncle of five segments ; 

 mouth-parts normal ; coxopodites of thoracic legs small, the last six pairs 

 movable ; first pair of pleopods similar in the two sexes, second pair 

 present in female ; uropods sub-terminal, biramous, styliform ; body more 

 or less laterally compressed, amj^hipod-like. 



Family Phreatoicidae. Phreatoicus, Chilton (Fig. 119); Phreatoi- 

 copsis, Spencer and Hall ; Phreatoicoides, Sayce. 



Sub-Order 3. Flabellifera, G. 0. Sars (1882). 



Abdominal somites free or more or less coalesced ; antennal peduncle 

 rarely with six segments ; mouth-parts often suctorial ; coxopodites of 

 thoracic legs more or less expanded into coxal plates, partially or com- 

 pletely fused with body ; first pair of pleopods similar in the two sexes, 

 second pair present in female ; uropods lateral, generally biramous, 

 lamellar, forming a caudal fan. 



Family Gnathiidae. Gnathia, Leach (Fig. 121) { = Anceus, Risso) 

 ((?), and Prauuft, Latreille ( $ and yg.) Family Anthuridae. Anthura, 

 Leach : Oyathura, Norman and Stebbing ; Paranthura, Bate and West- 

 wood ; Grurcgens, Chilton. Family Cymothoidae. (The following 

 sub-families are often ranked as families.) Sub-Family Cirolaninae 

 (Eurydicixae). Cirolana, Leach ; Eurydice^ Leach ; Conilera, Leach ; 

 Bathynormis, A, Milne-Edwards (Fig. 131). Sub-Family Anuropodinae. 

 Anuropus, Beddard; Bmnchuropus, Moore. Sub-Family E.\corallaninae. 

 Excomllana, Stebbing. Sub-Family Corallaninae. Corallana, Dana ; 



