96 



Forekomst og Udbredning. En Del Exemplarer af 



denne Art erholdes under Expeditionens sidste Togt paa 2 

 forskjellige Stationer, den ene (Stat. 290) beliggende om- 

 trent midt imellein Norge og Beeren Eiland, den anden 

 (Stat. 359) lige Vest ai' Spitsbergen; Dybden fra 191 til 

 416 Favne. Ingen af disse Stationer tilhører egentlig den 

 kolde Area. skjondt den sidste ligger lige ved Grændsen at' 

 samme. Om Artens Udbredning kan for Tiden kun siges 

 saa meget, at den ligger indenfor den arktiske Zone fra den 

 72de til den 78de Bredegrad. 



Trib. 3. Yalvifera. 



Anmærkninger. Inder denne Tribus sammenfatter 

 jeg de Isopoder. hos hvem sidste Par Bagkropslemmer eller 

 Halevedhængene er omformede til valvelformige Klapper, 

 der fra hver Side hvælver sig ud over de øvrige Bagkrops- 

 lemmer, saaledes at disse kommer til at ligge i en rummelig 

 af det skjoldformige Endesegment oventil (hekket Hule. 

 Den indeholder 2 distincte Familier. Arcturidæ og Idotheidæ, 

 hvoraf Repræseritanter nedenfor nærmere vil blive beskrevne. 



Favn. I. Arcturidæ. 



G-en. 1. Avctixi*us, Latr. l.S(>4. 

 Hist. nat. des Crustacés et des Insects. 



Slægtscharacteristik. Legemet af forholdsvis under- 

 sætsig Form. cvlindriskt eller tendannet. med 4de Forkrops- 

 segment kun lidet længere end de øvrige. 2det Par Foleres 

 Svøbe med simple, ikke saugtakkede Led. Iste Fodpar 

 forholdsvis lidet. med næstsidste Led smalt og forlænget. 

 sidste Led meget lidet. uden Klo. Hunnens Brystpose sam- 

 mensat af 3 Par tydelige Plader, tilhørende 2det— 4de For- 

 kropssegment. 



Bemærkninger. I den Begrændsning, hvori Slægten 

 lier tåges, indbefatter den foruden de 3 nedenfor nærmere 

 omtalte Former kun den af Miers 1 fra, Magellan-Strædet 

 beskrevne Ardurus Coppingeri. Alle de øvrige til denne 

 Slægt henførte Arter hører derimod ind under følgende 



1 Proceedines ol 



Sm-, ul London, .lau. -1. 1881. 



Oecurrence and Distribution. — Some fe w examples 

 of this species were obtained on the last cruise of the Ex- 

 pedition. at 2 different Stations, one (Stat. 290) located 

 about midway betvveen Norway and Beeren Eiland. the 

 otber (Stat. 359) due west of Spitzbergen ; depth ranging 

 from 191 to 41 (i fathoms. Neither of these Stations was 

 strictly within the cold area. although the latter lav in close 

 proximity to its boirndary. As regards the distribution of 

 the species. all that at present can be said amounts to the 

 fact of its oecurrence within the Arctic zone. from the 72nd 

 to the 78th parallel of latitude. 



Trib. 3. Valvifera. 



Remarks. - - AYithin this tribe 1 comprise all Isopods 

 in which the last pair of abdominal limbs or the caudal 

 appendages are transformed into valvular flaps. that. from 

 either side. arch out over the other pairs, in such manner 

 as to leave tbeni in a spacious cavity. covered above by 

 the scutiform terminal segment. It contains 2 distinct fam- 

 ilies - - the Arcturidæ and the Idotheidæ. of which re- 

 presentatives will be described in detail below. 



Inni. 1. Arcturidæ. 



Gen. 1. Ai-ctTii-vis, Latr. lsu4. 



Hist. nat. 



( Yustacrs et «Irs Insects. 



Generie Character. — Body comparatively thickset 

 in form. cylindric or fusiform. with the 4th segment but 

 little longer than the others. Flagellum of 2nd pair of an- 

 tenna' with simple, non-serrate joints. First pair of legs 

 comparatively small, with penultimate joint slender and 

 elongate. terminal joint exceedingly small, and without a ny 

 claw. Marsupium of female composed of 3 pairs of distinct 

 plates, belonging to 2nd. 3rd. and 4th pedigerous segments. 



Remarks. - Within the limits here assigned to the 

 genus, it comprises, exclusive of the 3 forms treated oi 

 in detail below. but one other species. Ardurus Coppingeri ', 

 from the Straits of Magellan, described by Miers. 1 All 

 the other species referred to this genus belong to the 



1 Proceedings of the /mil. Sm-, ut' London. Jan. 4th. 1881. 



