372 



Distribution. -- Arctic Ocean, widely distributed: Greenland (Kroyer), 

 Arctic America (Owen), Spitsbergen (Goes), the Murman Coast (Jarzynsky), 

 the White Sea (Lepechin), the Kara Sea (Hansen), the Siberian Polar Sea 

 (Stuxberg), Labrador (Packard), Atlantic Coast of North America (Sidn. 

 Smith). 



Fam. 13. Iphimedidae. 



External appearance much as in the Epimeridce. Cephalon produced 

 in front to a deflexed rostrum, postantennal corners not projecting. Coxal 

 plates well developed, the anterior pairs, as a rule, tapering to a point. Eyes 

 distinct. Antennae comparatively less slender than in the Epimerida, the 

 superior ones, as a rule, the longer, and without any accessory appendage. 

 Buccal area greatly projecting inferiorly, with the oral parts more or less 

 prolonged and peculiarly modified to adapt them for a semiparasitic life. 

 Gnathopoda rather unequal in structure and, as a rule, feeble, the anterior 

 ones being always extremely slender, and often exhibiting an approach to a 

 cheliform character. Pereiopoda normal, basal joint of the 3 posterior pairs 

 laminarly expanded. Last pairs of uropoda with the rami narrowly lanceolate 

 and edged with minute denticles. Telson unarmed, slightly incised at the tip. 



Remarks. - - The family is here taken in a somewhat more restricted 

 sense than as done by Boeck, who referred to it, besides the 3 following genera, 

 also the genus Laplnjstms of Kroyer, which latter I have found it necessary 

 to keep apart, as the type of a distinct family. In their external appearance 

 the forms belonging to the present family bear a considerable resemblance 

 to those of the EpimeridfC, differing however very markedly both in the struc- 

 ture of the gnathopoda and especially in that of the oral parts. The peculiar 

 modification of the latter organs seems to point to a semiparasitic nature of 

 these animals, and although hitherto only a single species, Ipimedia eblance 

 Sp. Bate, has been stated to be truly parasitic in habits, there is every reason 

 to believe that also the other Iphimedidse may, under certain circumstances, 

 lead a semiparasitic life. The family comprises as yet but 3 genera, alljrf 

 which are represented in the fauna of Norway. 



Gen. 1. Acanthonotosoma, Boeck, 187G. 



Syn : Acanthonotus, Owen. 

 ,, Vertumnus, White. 



Body more or less compressed, and distinctly carinated dorsally, the 

 carina being, as a rule, elevated to posteriorly pointing projections. Cephalon 



