CEUSTACEA OF XEW ZEALAND. 209 



importance from a systematic point of view, for we have great differences in this respect 

 in species of Idotea and in some of the Cymothoid;ie, and, on tlie whole, I think we must 

 place PhrcatoicMS somewhere near to the Asellidte, hut forming a separate family, the 

 Phreatoicidte, which bears to the Asellidse somewhat the same relation that the Caprcllidae 

 do to the Cyamidas in the Amphipoda. Limnoria may perhaps be placed, as is done by 

 many authors, in a separate family, the Limnoriidte, possessing some of the ancestral 

 characters of the Asellida?, and thus approaching nearer to the Phreatoicidse. Gerstaecker 

 puts Limnoria under the Sjihreronida?, hut forming a separate section, the Limnorhui 

 [45, p. 220]. 



Prom what has been already said it will be seen that Phreatoicus occupies a fairly 

 central position among the Isopoda, retaining to a greater extent than any others the 

 typical characters of the Isopoda. 



The following are the characters which I have provisionally advanced for the new 

 family Phreatoicida). These are simply given for the sake of comparison, and will no 

 doubt require revision when other forms allied to Phreatoicus are discovered : — 



Family PHPEATOICID.E. 



" Body subcylindrical, more or less laterally compressed. Mandibles with a well- 

 developed appendage. Legs distinctly^ divided into an anterior series of four and a 

 posterior series of three. Pleopoda broad and foliaceous and branchial in function, but 

 not protected by an operculum. Pleon * large, of six distinct segments. Uropoda 

 styUform." [26, p. 151.] 



Pamily ANTHURIDiE. 



Genus Cruregens, Chilton. 



(Transactions New Zealand Institute, vol. xiv. p. 175.) 



The following characters were assigned to this genus when I originally described it : — 

 " Body subcylindrical. Head small. First six thoracic segments subequal, the seventh 

 small and 'withont appendages. Antennte subequal, neither having a flagellum. First 

 pair of thoracic legs large and subchelate, the second and third subchelate but smoller ; 

 the three posterior pairs simple. First pair of abdominal appendages formmg an 

 operculum enclosing the branchial plates, last pair biramous. Telson squamiform." 



It is scarcely necessary^ to explain that the above description w^as drawn up by^ a tvro 

 in the study of the Crustacea, and that though modelled on the descriptions given by 

 others of allied genera, it contains much that is unnecessary and little that is essential. 



The genus appears to fall under Norman and Stebbing's [106] " Section B," though 

 the mouth-parts are even more modified than in the species assigned to this section by 

 these authors. The following generic diagnosis may be given for the sake of comjiarison 



* I have substituted " pleoii '" for " abdomen,"' which I had inadvertently put Ln my original diagnosis. 



