The Isopods of Abyssal Depths in the Atlantic Ocean

Distribution: Known only from type locality.
Affinities: Close to gracilipes but with the anterolateral
angle of the fifth peraeonal somite pointed
rather than rounded.
Desmosoma intermedium Hult
Figure 50 H-J
Synonyms: Desmosoma intermedium Hult, 1936, pp.
2-6, Figs. 1-21; — 1941, pp. 80-84.
Diagnosis: Desmosoma without a spine at each
postero-lateral angle of the pleon but with lateral
margins serrated. Frons of cephalon concave at apex.
Coxal plates triangular and minute, not strongly
produced. First peraeonal somite slightly shorter
than second. First peraeopod weak without stout
setae. Uropoda biramous.
Measurements: None available.
Type locality: Koster Fjord, off Vattenholm, 206
meters, temperature 6.2° C. (Hult, 1936).
Distribution: North Atlantic, Norway, Kattegat,
100 meters to 2258 meters, and Ingolf Station 24,
latitude 63° 06' N., longitude 56° 00' W., 2258 meters.
Affinities: Looking much like D. elongatum Bonnier
but with uniramous uropods.
Desmosoma coarctatum (Hansen) G. O. S.
Figure 50 K
Synonyms: Eugerda coarctata G. O. Sars, 1899, p.
253, Desmosoma natator Hansen, 1916, p. 115; —
Gurjanova 1933, p. 418. Desmosoma coarctatum (G. O.
Sars), Hult 1936, p. 10; — 1941, pp. 86-88 and
references.
Diagnosis: Desmosoma with a spine at each posterolateral
angle of pleon. Frons of cephalon straight at
apex. Coxal plates slightly produced, bilobed. First
and second peraeonal somites subequal in length.
Fifth with a long spine at each antero-lateral angle.
First peraeopod stout, with stout seta. Uiopoda
uniramous.
Measurements: Female length 2.0 mm., male 1.5
mm. (G. O. Sars, op. cit., p. 253).
Type locality: North Atlantic, Skager Rak, north
of Skagen, 125 fathoms (G. O. Sars, op. cit., p. 250).
Distribution: Besides the Skager Rak (Hult, 1941)
the species was found at Davis Strait, Ingolf Station
36, latitude 61° 50' N., longitude 56° 21'W., 2702
meters, temperature 1.5° C, one specimen (Hansen,
op. cit., p. 116).
Affinities: This species is unique in having the
stout spines at the antero-lateral angles of the fifth
peraeonal somite.
Desmosoma longispinum Hansen
Figure 50 L-M
Synonyms: Desmosoma longispinum Hansen, 1916, pp.
111-112, PL 10.
ABYSSAL ATLANTIC ISOPODS 165
Diagnosis: Desmosoma with a long spine at each
postero-lateral angle of the pleon. Frons of cephalon
rounded slightly at apex. Coxal plates elongated,
strongly produced forward, over twice as long as wide,
and pointed at apex. First and second peraeonal
somites subequal in length. First peraeopods weak;
without stout setae. Uropods uniramous.
Measurements: Female length 2.1 mm., male 1.8
mm. (Hansen, op. cit.).
Type locality: North Atlantic, south of Davis
Strait, Ingolf Station 38, latitude 59° 12' N.,
longitude 51° 05' W., 3521 meters, 4 specimens
(Hansen, op cit.).
Distribution: Known only from type locality.
Affinities: This species is close to magnispinum but
has the lateral borders of the peraeonal somites
6-7 straight rather than rounded.
Desmosoma striata, new species
Figure 51 A-F
Synonyms: Non e.
Diagnosis: Desmosoma without spines at each postero-lateral
border of pleon. Pleon evenly rounded,
lacking serrations. Coxal plates bilobed. First and
second peraeonal somites subequal in length. First
with stout spines at antero-lateral angle. Fifth
without spines at antero-lateral angles. Structure of
first peraeopod not known. Uropods uniramous.
Measurements: Female with oostegites length 1.4
mm., width pleon 0.2 mm.
Type locality: North Atlantic, L.G.O. Biotrawl
No. 17, type only, cat. no. 1-179.
Distribution: Known only from type locality.
Affinities: Because of the absence of the first peraeopods
it is difficult to determine the affinities of this
species. The stout spines at the first peraeonal somite
are distinctive.
Desmosoma magnispinum, new species
Figure 51 G-J
Synonyms: None.
Diagnosis: Desmosoma with a pronounced long
spine at postero-lateral angle of pleon. Coxal plates
much elongated, pointed. First and second peraeonal
somites subequal in length. Fifth without spines at
antero-lateral angles. Lateral borders of sixth and
seventh semicircular. First peraeopod weak, without
stout setae. Uropods uniramous.
Measurements: Holotype male length 2.1 mm.,
width pleon 0.25 mm.
Type locality: North Atlantic, Bay of Panama,
L.G.O. Biotrawl No. 103, type only, cat. no. 1-176.
Distribution: Known only from type locality.
Affinities: This species is similar to D. longispinum
Hansen, from which it differs in having semicircular
lateral borders to peraeonal somites 6-7.