The Isopods of Abyssal Depths in the Atlantic Ocean

Diagnosis: Frontal border of cephalon excised
with a broad low median projection. Pleon and peraeon
lateral margins continuous. Flagellum of first
antenna with five articles. Postero-lateral angles of
pleon slightly exceeding median margin. Dorsum
of pleon with a pair of slight short ridges above
uropodal insertion. First article of peduncle of first
antenna concealed from dorsal view by cephalon.
Uropods not extending to postero-lateral margin of
pleon. Antero-lateral margins of fourth peraeonal
somite not produced forward.
Measurements: Holotype female length 3.6 mm.,
width pleon 1.3 mm.
Type locality: South Atlantic, holotype female,
plus two female paratypes, L.G.O. Biotrawl No.
53, cat. no. 1-21.
Distribution: Known only from type locality.
Affinities: This species is allied to H. princeps, but
the uropoda extend to the posterior margin of the
pleon at the postero-lateral angles.
Haploniscus acutus, new species
Figure 11 A-C
Synonyms: None.
Diagnosis: Frontal border of cephalon excavate,
entire. Pleon inset from peraeonal lateral margin.
Flagellum of first antenna with five articles.
Postero-lateral angles of pleon projecting beyond
medial pleonal margin. Dorsum of pleon smooth.
First article of first antenna not concealed by cephalon.
Uropods not extending to postero-lateral margin of
pleon. Antero-lateral angles of fourth peraeonal
somite not produced forward.
Measurements: Holotype female length 3.3 mm.,
width pleotelson 1.2 mm.
Type locality: South Atlantic, holotype female,
L.G.O. Biotrawl No. 51, cat. no. 1-13.
Distribution: Known only from type locality.
Affinities: Closely related to H. spinifer Hansen,
but with the uropoda much longer—that is, extending
almost to the tip of the postero-lateral angles of the
pleon.
Haploniscus parallelus, new species
Figure 11 D-H
Synonyms: None.
Diagnosis: Frontal margin of cephalon convex,
entire. Pleon set in from lateral margins of peraeon.
Flagellum of first antenna with four articles.
Postero-lateral angles of pleon not projecting beyond
medial pleonal margin. Dorsum of pleon smooth.
First article of first antenna concealed by cephalon.
Rami of sympod of first male pleopod joined at apex.
Uropods extending beyond posterior margin of
pleon. Antero-lateral angles of fourth pleonal somite
oroduced forward.
ABYSSAL ATLANTIC ISOPODS 103
Measurements: Holotype male length 1.8 mm.,
width pleon 0.55 mm., allotype length 2.1 mm., width
pleon 0.6 mm.
Type locality: South Atlantic, types plus one female
and two fragmentary paratypes, L.G.O. Biotrawl No.
12, cat. no. 1-2.
Distribution: Also taken from L.G.O. Biotrawl
No. 52, two females, cat. no. 1-3.
Affinities: This species is related to H. tuberculatus,
but has the pleonal margin set in from the peraeonal
margin.
Haploniscus capensis, new species
Figure 11 I-K
Synonyms: None.
Diagnosis: Frontal border of cephalon excavated
and with very short trifid projection medially. Pleon
set in from peraeon. Flagellum of first antenna
with five articles. Postero-lateral angles of pleon
projecting beyond medial pleonal margin and are
medially recurved. Dorsum of pleon with short
carinae above uropods. First article of first antenna
not concealed by cephalon. Rami of male first
pleopods not separated at apex. Uropods not extending
to posterior margin of pleon. Antero-lateral
angles of fourth pleonal somite not produced forward.
Measurements: Holotype male length 2.9 mm.,
width pleotelson 0.5 mm., allotype gravid length
2.7 mm., width pleotelson 1.1 mm., and nine male,
ten female, one juvenile paratypes.
Type locality: South Atlantic, types only, L.G.O.
Biotrawl No. 55, cat. no. 1-25.
Distribution: Known only from type locality.
Affinities: This species resembles H. tridens in many
respects, differing from it in having the lateral borders
of the peraeon and pleon discontinuous.
Haploniscus trituberculatus, new species
Figure 11 L-Q,
Synonyms: None.
Diagnosis: Frontal border of cephalon excavate,
entire. Pleon set in from peraeon. Flagellum of first
antenna with four articles. Postero-lateral angles of
pleon not projecting beyond medial pleonal margin.
Dorsum of pleon with two tubercles located on anterior
third of pleon and a large dorsally indented
swelling medially near posterior margin. First article
of first antenna concealed by cephalon. Rami of
male first pleopods not separated at apex. Uropods
concealed, extending to posterior margin of pleon.
Measurements: Holotype male length 2.25 mm.,
width pleotelson 0.55 mm., allotype length 2.6 mm.,
width pleotelson 0.7 mm., plus two male, three female,
and two fragmentary paratypes.
Type locality: South Atlantic, types, L.G.O.
Biotrawl No. 51, cat. no. 1-24.