The Isopods of Abyssal Depths in the Atlantic Ocean

not extending to postero-lateral margin of pleon.
Rami of sympod of male first pleopoda separated.
Antero-lateral border of fourth peraeonal somite
strongly produced forward.
Measurements: Holotype male length 2.1 mm.,
width pleon 0.6 mm.
Figure 9. A-D: Haploniscus elevatus, n. sp. A:
dorsal view male; B: first pleopod; C: first
antenna; D: anus and uropod. E-G: Haploniscus
quadrifrons, n. sp. E: dorsal view male
type; F: first antenna; G: first pleopod.
Type locality: South Atlantic, holotype and two
fragments from L.G.O. Biotrawl No. 22, cat. no. 1-16.
Distribution: Also found at L.G.O. Biotrawl No.
23, one male, cat. no. 1-17.
Affinities: This species is closely allied to H.
princeps and H. elevatus, from which it is distinguished
by the two dorsal tubercles on the pleon.
Haploniscus princeps, new species
Figure 10 A-C
Synonyms: None.
Diagnosis: Frontal border of cephalon excised,
•vith a median slight but wide projection. Pleon
ABYSSAL ATLANTIC ISOPODS 101
set in from peraeon. Flagellum of first antenna with
four articles. Postero-lateral angles of pleon projecting
beyond medial margin. Dorsum of pleon
smooth. First article of peduncle of first antenna not
concealed by cephalon. Uropods not extending to
postero-lateral border of pleon. Rami of sympod of
male first pleopod joined at apex. Antero-lateral
margins of fourth peraeonal somite produced forward.
Measurements: Holotype female length 2.1 mm.,
width pleotelson 0.65 mm. Male allotype length 2.2
mm., (fragment).
Type locality: South Atlantic, types plus three
female paratypes, L.G.O. Biotrawl No. 53, cat. no.
1-14.
Distribution: Also found at L.G.O. Biotrawl No.
14, eleven females and one male, cat. no. 1-203.
Affinities: H. princeps is closely allied to H. elevatus,
H. nondescriptus, and H. quadrifrons. The absence of
dorsal tubercles on the pleon and the short uropoda
distinguish it.
Haploniscus percavix, new species
Figure 10 D-E
Synonyms: None.
Diagnosis: Frontal border of cephalon straight
but with minute medial knob. Lateral margins of
pleon and peraeon continuous. Flagellum of first
antenna with five articles. Postero-lateral angles of
pleon projecting beyond medial margin. Dorsum of
pleon smooth. First article of first antenna not concealed
by cephalon. Uropods extending to posterior
margin of pleon. Antero-lateral angles of fourth
peraeonal somite not produced forward.
Measurements: Male holotype intersex length 2.4
mm., width pleotelson 0.7 mm., female allotype
length 3.4 mm., width pleotelson 1.5 mm.
Type locality: South Atlantic, types plus one male
intersex paratype, L.G.O. Biotrawl No. 53, cat. no.
1-6.
Distribution: Also found at L.G.O. Biotrawl No.
16, one male, one female, cat. no. 1-7, and North
Atlantic, Atlantis Station 15, one female, cat. no. 1-207.
Affinities: This species is related to H. retrospinis
Richardson, from which it differs in having the
postero-lateral angles of the pleon two times the length
of the uropoda.
Haploniscus tricornis, new species
Figure 10 F-I
Synonyms: None.
Diagnosis: Frontal border cephalon excavate
but with a medial apically trifid projection. Lateral
margins of pleon and peraeon continuous. Flagellum
of first antenna with six articles. Postero-lateral
angles of pleon not projecting beyond medial pleonal