The Isopods of Abyssal Depths in the Atlantic Ocean

logical choice of type locality; latitude, 58° 10' N.,
longitude 48° 25' W., 3474 meters, temperature
1.4° C, four specimens.
Distribution: Uncertain. It was collected from
North Atlantic, Ingolf Station 22; South Atlantic,
L.G.O. Biotrawl No. 18, one female, one male, cat.
no. 1-22, and L.G.O. Biotrawl No. 16, three females,
cat. no. 1-23.
Affinities: This species appears to be most closely
related to acutus, n. sp.
Haploniscus minutus, new species
Figure 7 A-C
Synonyms: None.
Diagnosis: Frontal border excised, entire. Pleon
and peraeonal lateral borders continuous. Flagellum
of first antenna with six articles. Postero-lateral
angles of pleon not projected beyond medial margin.
Dorsum of pleon smooth. First article of first antenna
not concealed by cephalon. Uropoda extending
beyond posterior medial margin of pleon. Anterolateral
borders of fourth pleonal somite not projected
forward. Dorsum of head not tuberculate.
Measurements: Holotype female length 2.5 mm.,
width pleon 0.8 mm.
Type locality: South Atlantic, L.G.O. Biotrawl
No. 12, one female, cat. no. 1-15.
Distribution: Known only from type locality.
Affinities: The species is close to H. excisus,
differing markedly from it in having the lateral
borders of the pleon and peraeon continuous.
Haploniscus spatulifrons, new species
Figure 7 D-H
Synonyms: None.
Diagnosis: Frontal border deeply excavate and
with a pronounced pointed spatulate projection. Pleon
and peraeon lateral borders continuous. Flagellum
of first antenna with five articles. Postero-lateral
angles of pleon not produced beyond medial margin.
Dorsum of pleon smooth. First article of first antenna
not concealed by cephalon. Uropods not extending
to posterior border of pleon. Rami of sympod of male
first pleopod round at apex. Antero-lateral borders of
fourth peraeonal somite not produced forward.
Measurements: Holotype male length 5.3 mm.,
width pleon 2.0 mm. Allotype female length 2.6 mm.,
width pleon 0.9 mm.
Type locality: South Atlantic, types and only
specimens from L.G.O. Biotrawl No. 51, cat. no. 1-10.
Distribution: Known only from type locality.
Affinities: The species is perhaps most nearly
allied to H. bicuspis (G. O. Sars), but its spatulate
rostrum distinguishes it.
ABYSSAL ATLANTIC ISOPODS 99
Haploniscus tuberculatum, new species
Figure 7 I-K
Synonyms: None.
Diagnosis: Frontal border of cephalon convex,
entire. Lateral borders of pleon and peraeon continuous.
Flagellum of first antenna with four articles.
Postero-lateral angles of pleon not projecting beyond
medial margin. Dorsum of pleon tuberculate. First
article of first antenna concealed by cephalon.
Uropods extending beyond posterior margin of pleon.
Antero-lateral borders of fourth peraeonal somite not
produced forward.
Measurements: Holotype female length 1.7 mm.,
width pleon 0.4 mm.
Type locality: South Atlantic, type and only specimen
collected from L.G.O. Biotrawl No. 51, cat. no.
1-20.
Distribution: Known only from type locality.
Affinities: This species is most nearly related to
H. parallelus, n. sp., from which it differs in having the
lateral borders of the pleon and peraeon continuous.
Haploniscus tridens, new species
Figure 8
Synonyms: None.
Diagnosis: Frontal border deeply excavate and
with a sharp trifid median projection. Pleon and
peraeon lateral borders continuous. Flagellum of
first antenna with five articles. Postero-lateral margins
of pleon produced beyond medial margin.
Dorsum of pleon smooth. First article of first antenna
not concealed by cephalon. Uropods extending to
posterior border of pleon. Rami of sympod of male
first pleopod separated slightly at apex. Anterolateral
borders of fourth peraeonal somite not produced
forward.
Measurements: Male holotype length 3.2 mm.,
width pleotelson 1.6 mm., allotype 4.2 mm. length,
width pleotelson 2.0 mm.
Type locality: South Atlantic, types and one fragment
from L.G.O. Biotrawl No. 12, cat. no. 1-1.
Distribution: Known from type locality and from
South Atlantic, L.G.O. Biotrawl No. 212, one intersex,
cat. no. 1-59, one intersex, cat. no. 1-61.
Affinities: The species is most closely allied to
H capensis, n. sp., differing from it most obviously in
having the lateral borders of the pleon and peraeon
continuous.
Haploniscus elevatus, new species
Figure 9 A-D
Synonyms: None.
Diagnosis: Frontal border excavate with a very
slight, wide medial lobe. Pleon strongly set in from