NO. 3 BARNARD : THE PHOXOCEPHALIDAE 293 



Genus Phoxocephalus Stebbing 



Phoxus Kroyer 1842: 150 (not Billberg 1820, Coleoptera). 

 Phoxocephalus Stebbing 1888: 810-811 (new name). 



Diagnosis. — Molar process of mandible well developed, ridged and 

 cuspate apically; third uropods with slender, elongated rami. 



Type species. — Phoxus holbolli Kroyer 1842. 



Remarks. — This group of species is the only assemblage in the 

 family which is characterized by the ridged molar of the mandible, 

 except for the genus J oubinella. 



It is a genus which includes several different species-groups and 

 therefore may be polyphyletic and quite artificial. The groups are as 

 follows : 



(1) The type species, P. holbolli, lacks eye lenses and has rather 

 small gnathopods. Atlantic Ocean. 



(2) Four species, P. bassi, P. regium, P. kergueleni and P. homilis, 

 differ from the type species by the presence of lensed eys, and enlarged, 

 eusirid-type gnathopods. Pacific, Indian and Antarctic Oceans. 



(3) P. tcnuipes lacks eye lenses but has enlarged gnathopods; it 

 has an elongated fourth peraeopod, a minor difference. North Atlantic. 



(4) P. coxalis is unusual in having a slender second article on the 

 third peraeopod, a character often used for generic separation ; gnathopods 

 enlarged. South Atlantic Ocean. 



I believe that it is premature to stratify these groups with different 

 names. However, there may be future zoogeographic evidence which 

 will verify a more distant relationship between these groups than now 

 shown by their morphologies. The two North Atlantic species show 

 the stepwise loss of eye lenses (tenuipes and holbolli) and reduction 

 of gnathopod size {holbolli) which may be evidence of long isolation 

 from more primitive Pacific elements, bearing eye lenses and enlarged 

 gnathopods. 



Other generic features. — Palp of maxilla 1 uniarticulate, palp of 

 maxilliped with long fourth article bearing a short terminal seta; 

 second antenna of male as long as body; posterior edge of peraeopod 

 5, article 2, poorly sculptured. 



Note on P. capuciatus. — Oliveira 1955 has described a new species 

 Phoxocephalus capuciatus, which should be removed to Platyischnopus 

 gracilipes Schellenberg 1931 in the Haustoriidae. 



