The Isopods of Abyssal Depths in the Atlantic Ocean

peduncles narrow and curved forward in front of
cephalon, ocelli lacking.
Composition: Known from type species and the one
other new species described herein. Pleurogonium
pulchrum Hansen possibly belongs to this genus.
Notoxenoides abyssi, new species
Figure 58
Synonyms: None.
Diagnosis: Notoxenoides with a produced, pointed,
spinulate pleon. Flagellum of first antenna with
four articles. Dorsum of pleon without spines,
lateral border spinulate. Propod with only a stout
seta on inferior margin. Ocular peduncles projecting
in front of cephalon. Second article of peduncle of
first antenna with a spine at distal outer margin.
Measurements: Length holotype male 1.9 mm.,
width pleotelson 0.44 mm., length gravid allotype
2.0 mm., width pleotelson 0.5 mm.
Type locality: South Atlantic, L.G.O. Biotrawl
No. 54, types plus two male and one female paratypes,
cat. no. 1-181.
Distribution: Known only from type locality.
Affinities: The species resembles Pleurogonium pul-
Diagnosis: Paraselloidea with free cephalon. Eyes
lacking, mandible with tapering yet blunt molar, palp
present. Uropod with long peduncle. None of the
peraeopods modified for swimming; dactyl of sixth
with two claws. Last two articles of maxillipedal palp
one-half the width of first three; second \ the width of
endite. Somites of peraeon much wider than long.
Pleon with two somites.
Composition: The family probably contains Jolanthe
Beddard, Microprotus Richardson, and Katianira
Richardson. Janthopsis and Rhacura probably belong
to the Ianirellidae (Menzies, in press). The family is
related to the Ianirellidae, but the maxillipedal palp
articles are too narrow and it has two somites to the
pleon instead of only one. The very long uropodal
peduncle characterizes members of the family.
Genus: ACANTHASPIDIA Stebbing
Type species: Acanihoniscus typhlops G. O. Sars,
1879, p. 434.
Synonym: Acanthoniscus G. O. Sars, 1879, p. 434,
— 1885, p. 119, PI. X. Acanthaspidia Stebbing, 1893,
p. 378.
Diagnosis: Acanthaspididae with mandible having
triarticulate palp and lacinia and setal row. Uropoda
biramous, with long peduncle, insertion terminal.
Maxillipedal palp with expanded first three articles all
ABYSSAL ATLANTIC ISOPODS 177
chrum Hansen, 1916, in having the dorsal spines on the
body. The mandibles would obviously distinguish
the two, but Hansen did not describe them for
pulchrum. Its nearest abyssal relative is the following
new species.
Notoxenoides vemae, new species
Figure 59
Synonyms: None.
Diagnosis: Notoxenoides with apex of pleon pointed
but not strongly produced. Flagellum of first antenna
with four articles. Dorsum of pleon without spines,
lateral border spinulate. Propod with a curved spine
and one stout seta on inferior margin. Ocular
peduncles (?) directed laterally. Second article of
peduncle of first antenna without spines.
Measurements: Female holotype length 1.8 mm,
width at widest point 0.8 mm.
Type locality: South Atlantic, L.G.O. Biotrawl No.
18, type only, cat. no. 1-174.
Distribution: Known only from type locality.
Affinities: Related to N. abyssi Menzies and P.
pulchrum Hansen, but with sharp laterally directed
ocular peduncles.
ACANTHASPIDIDAE, new family
less than one-half the width of endite. Cephalon
without eyes or eye stalks. Peraeonal somites provided
with spine-like lateral expansions. Coxal plates
visible in dorsal view on somites 5-7 inclusive. Pleonal
lateral margin with many spine-like projections.
Composition: The genus contains three species
besides the new one described here:
Depth Range (Meters)
Species Least Greatest
1. typhlops (G. O. Sars) 823 1354
2. decorata (Hansen, 1895) 4000 4000
3. drygalskii Vanhoffen 350 385
A KEY TO THE SPECIES OF
ACANTHASPIDIA
1. Body with a single median row of single spines . . 2
1. Body with a pair of spines on
midline drygalskii Vanhoffen
2. Frons bifid 3
2. Frons with single frontal horn . . . . decorata Hansen
3. Lateral border fifth peraeonal somite
trifid typhlops (G. O. Sars)
3. Lateral border of fifth peraeonal somite
with one large spine and a small one . bifurcata, n.sp.
Acanthaspidia bifurcata, new species
Figure 60
Synonyms: None.
Diagnosis: Acanthaspidia with bifurcating rostrum,