90 
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 imellem Norge og Beeren Eiland, den anden 
(Stat. 359) lige Vest af Spitsbergen; Dybden fra 191 til 
416 Favne. Ingen af disse Stationer tilhorer egentlig den 
kolde Area, skjondt den sidste ligger lige red G rsendsen af 
samme. Om Arteus Udbredning kan for Tideu kun siges 
saameget, at den ligger indenfor den arktiske Zone fra den 
72de til den 78de B redegrad. 
Trib. 3. Valvifera. 
Anmserkninger. Under denne Tribus sammenfatter 
jeg de Isopoder. lios hvem sidste Par Bagkropslemmer eller 
Halevedluengene er omformede til valvelformige Klapper. 
der fra liver Side hvadver sig ud over de pvrige Bagkrops- 
lemmer, saaledes at disse kommer til at ligge i eu rummelig 
af det skjoldformige Endesegment oventil dsekket Hule. 
Den indeliolder 2 distincte Familier. Arcturida> og Idotbeidm, 
hvoraf Reprsesentanter nedenfor mermere \'il blive beskrevne. 
Fain. 1. Arcturidse. 
Gen. 1 . Arcturus, Latr. 1804. 
Hist. nat. des Crustacea et des Insects. 
Slsegtscharacteristik. Legemet af forholdsvis under- 
ssetsig Form, cylindriskt eller tendannet, med 4de Forkrops- 
segment kun lidet lamgere end de ovrige. 2det Par Foleres 
Svpbe med simple, ikke saugtakkede Led. lste Fodpar 
forholdsvis lidet, med nsestsidste Led smalt og forlamget, 
sidste Led meget lidet, uden Klo. Hunnens Brvstpose sam- 
mensat af 3 Par tydelige Plader. tilhorende 2det— 4de For- 
kropssegment. 
Bemserkninger. I den Begramdsning, hvori Slmgten 
her tages, indbefatter den foruden de 3 nedenfor nmrmere 
omtalte Former kun den af Miers 1 fra Magellan-Straedet 
beskrevne Arcturus Coppingeri. Alle de ovrige til denne 
Slsegt henforte Arter hprer derimod ind under fplgende 
1 Proceedings of the Zoo!. Soc. of London, Jan. 4, 1881. 
Occurrence and Distribution. — Some few examples 
of this species were obtained on the last cruise of the Ex- 
pedition. at 2 different Stations, one (Stat. 290) located 
about midway between Norway and Beeren Eiland, the 
other (Stat. 359) due west of Spitsbergen; depth ranging 
from 191 to 416 fathoms. Neither of these Stations was 
strictly within the cold area, although the latter lay in close 
proximity to its boundary. As regards the distribution of 
the species, all that at present can be said amounts to the 
fact of its occurrence within the Arctic zone, from the 72nd 
to the 78th parallel of latitude. 
Trib. 3. Valvifera. 
Remarks. — - Within this tribe I 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 them in a spacious cavity, covered above by 
the scutiform terminal segment. It contains 2 distinct fam- 
ilies — the Arcturida? and the Idotheidte. of which re- 
presentatives will be described in detail below. 
Fain. 1. Arcturidse. 
Gen. 1. Arcturus, Latr. 18U4. 
Hist, nat. des Crustacea et des Insects. 
Generic 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- 
tennae with simple, non-serrate joints. First pair of legs 
comparatively small, with penultimate joint slender and 
elongate, terminal joint exceedingly small, and without any 
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 of 
in detail below, but one other species. Ardums 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 Zool. Soc. of London, .Tan. 4th, 1881. 
