The Isopods of Abyssal Depths in the Atlantic Ocean

Type locality: North Atlantic, L.G.O. Biotrawl No.
7, type only, cat. no. 1-191.
ABYSSAL ATLANTIC ISOPODS 183
Distribution: Known only from type locality.
Affinities: Unique.
Family: ECHINOTHAMBEMIDAE Menzies
Synonyms: Echinothambemvdae Menzies, 1956a, pp.
9-10.
Diagnosis: Paraselloidea with fused or free head,
eyes lacking. Mandibles normal, molar process well
developed and expanded a truncated apex. Antennae
shorter than body, about twice the length of cephalon.
All peraeopods simple, 2-7 simple walking legs; dactyl
with two terminal claws. Uropoda terminal with
peduncle. Last one or two peraeonal somites fused
with pleon. First three articles of maxillipedal palp
expanded, as wide as endite. Coxal plates lacking.
First peduncular article of first antenna much
expanded. Anus contained within the branchial
chamber.
Composition: Formerly monotypic (Menzies, 1956a,
p. 10). A new genus is added here and the diagnosis
has accordingly been altered to allow its inclusion.
Genus: ECHINOTHAMBEMA Menzies
Type species: Echinothambema ophiuroides Menzies
1956a, p. 11.
Synonyms: Echinothambema Menzies, 1956a, pp.
10-11.
Diagnosis: Same as for family. Mandible without
palp.
Composition: One abyssal Atlantic species.
Echinothambema ophiuroides Menzies
Figure 62 N-O
Synonyms: Echinothambema ophiuroides Menzies,
1956a, p. 11.
Diagnosis: Echinothambema with first antenna with
six articles, last one-third longer than penultimate
article. Lateral borders of peraeonal somites each
with expanded and pronounced margin bearing a
single stout seta. Body sharply granulate. Maxilliped
with two coupling hooks. Cephalon at antero-lateral
Diagnosis: Paraselloidea with cephalon free, eyes
lacking. Mandibles normal, molar process well
developed and expanded at truncated apex. Antennae
shorter than body. All peraeopods simple walking
legs, dactyls with two terminal claws. Uropod absent.
Pleon with one somite only. All peraeonal somites
distinct. First three articles of maxillipedal palp as
wide as endite. Coxal plates lacking.
margin with a pair of swellings, each bearing a stout
seta. Mandibles without a palp.
Measurements: Holotype ambisexual 5.00 mm.
long, 1.5 mm. wide.
Type locality: North Atlantic, L.G.O. Biotrawl
No. 1, type only, cat. no. 11760 A.M.N.H.
Distribution: Known only from type locality.
Affinities: Unique.
VEMATHAMBEMA, new genus
Type species: Vemathambema elongata, new species.
Synonyms: None.
Diagnosis: Echinothambemidae with cephalon
fused to first peraeonal somite and last somite of
peraeon fused to pleon. First article of first antenna
not expanded but stout and elongated as long as
second.
Composition: Monotypic abyssal.
Affinities: Related to Echinothambema in the absence
of coxal plates and the fusion of peraeonal
somite 7 with the pleon and in the absence of a
mandibular palp. Uropoda (missing) probably with
peduncle.
Vemathambema elongata, new species
Figure 62 J-M
Synonyms: None.
Diagnosis: Vemathambema with smooth pleon, apex
rounded, body without spines or setae. Frons of
cephalon concave, devoid of spines or setae
Measurements: Holotype female length 5.2 mm
width pleon 0.9 mm.
Type locality: South Atlantic, L.G.O. Biotrawl
No. 15, type only, cat. no. 1-112.
Distribution: Known only from type locality.
Affinities: Unique.
Family: THAMBEMATIDAE
Composition: Monotypic. The family resembles
the Jaeropsidae in many significant respects,
notably in the details of the structure of the
maxillipeds and the shape of the front of the
head and the antennae structure. The mandibular
structure, however, clearly indicates its distinctiveness.