The Isopods of Abyssal Depths in the Atlantic Ocean

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ROBERT J. MENZIES Figure 60. Acanthaspida bifurcata, n. sp. A: in toto, type; B: third pleopod of female; C: uropodal rami; D: first antenna; E: maxilliped; F: first peraeopod; G: fifth peraeopod; H: apex of molar of right mandible; I: right mandible; J: ventral surface of pleotelson. first six peraeonal somites each with a mid-dorsal spine. Last three peraeonal somites with one spinelike lateral expansion and smaller tooth. Each lateral border of pleon with seven spine-like projections alternating in size. Maxilliped with two coupling hooks. Flagellum of first antenna with eight articles. Measurements: Holotype female length 4.2 mm., width pleotelson 1.5 mm., and one fragmentary female paratype. Type locality: South Atlantic, L.G.O. Biotrawl No. 16, types only, cat. no. 1-216. Distribution: Known only from type locality. Affinities: Related to typhlops but with fewer peraeonal spine-like lateral extensions. Acanthaspidia decorata Hansen Figure 61 A Synonyms: Acanthaspidia decorata Hansen, 1895, pp. 6-7, PI. I. Diagnosis: Acanthaspidia with mid-frontal projection a simple spine. Each peraeonal somite with a
ingle mid-dorsal spine except fourth, which has two. iach lateral border of pleon with eight spines; apex oncave. Lateral borders of somites 5—7 with only ne large spine-like extension. Flagellum of first mtenna with ten or more articles. Measurements: Male length 9.7 mm. (Hansen, op. •it.). Type locality: Plankton Expedition, North Atlan- Synonyms: Abyssianiridae Menzies, 1956a, pp. 12- .3. Diagnosis: Paraselloidea with free head. Manlibles normal, molar process expanded and truncated it apex. First antenna shorter than body. Peraeonal >omites all of similar length, none fused. Peraeopods 2-7 -simple walking legs, two claws on dactyls, not :hree, no legs modified for swimming. First peraeopod prehensile. Coxal plates rounded, not spiniform, visible in dorsal view. Pleon with two somites. Uropoda biramous, inserting dorsally with short peduncle. Maxillipedal palp with first three articles as wide as endite. (Modified after Menzies, 1956a.) Composition: Formerly this family contained only the type genus. It is now possible to add one new genus, Xostylus, with a single new species. The family is closely allied to the Munnidae through the genus Austrosignum, which may ultimately have to be transferred to the Abyssianiridae. Genus: ABYSSIANIRA Menzies Synonyms: Abyssianira Menzies, 1956a, p. 14. Type species: Abyssianira dentifrons Menzies, 1956a, p. 15. Diagnosis: Abyssianiridae with coxal plates visible in dorsal view on peraeonal somites 2-7 inclusive. Lateral margins of cephalon flattened and expanded. Abyssianira dentifrons Menzies Figure 61 B-H Synonyms: Abyssianira dentifrons Menzies, 1956a, p. 15. Diagnosis: Abyssianira with denticulate body margins. Cephalon expanded, flattened rostrum, and lateral horns. Pleotelson lateral border denticulate, I apex rounded. First antenna with six articles, last about one-third shorter than penultimate article. Male first pleopod with three setae at each angle on either side of sympod. Maxilliped with two coupling hooks. Mandible with triarticulate palp, last article with two apical setae. Uropodal exopod one-half the length of endopod. ABYSSAL ATLANTIC ISOPODS 179 Family: ABYSSIANIRIDAE Menzies tic, Station 158, latitude 7.5° N., longitude 21.3° W., 4000 meters. Distribution: Known only from type locality. It was not collected by Vema. Affinities: The simple spine at the frons of the cephalon and the concave apical margin on the pleon distinguish this species. Measurements: Holotype male length 2.75 mm., width at second peraeonal somite 0.85 mm. Type locality: North Atlantic, L.G.O. Biotrawl No. 1, type only, cat. no. 11762 A.M.N.H. Distribution: Also found at South Atlantic, L.G.O. Biotrawl No. 214, one female, cat. no. 1-203; L.G.O. Biotrawl No. 12, one male, two females, cat. no. 1-90.; L.G.O. Biotrawl No. 51, one fragment, cat. no. 1-185. Affinities: This species is closely allied to A. argentenensis, from which it differs in having the apex of the pleon smooth, not spinulate. Abyssianira argentenensis, new species Figure 61 I-L Synonyms: None. Diagnosis: Abyssianira with quadrate pleotelson. First antenna with six articles, last article subequal in length to penultimate article. Propod of first peraeopod with only one stout two-pointed seta. Apex of pleon spinulate. Uropodal exopod two-thirds the length of endopod. Measurements: Holotype female length 1.5 mm., pleon 0.5 mm. Type locality: North Atlantic, holotype, L.G.O. Biotrawl No. 207, cat no. 1-218. Distribution: Known only from type locality. Affinities: Closely related to A. dentifrons, from which it differs in having the apex of the pleon spinulate. XOSTYLUS, new genus Type species: Xostylus parallelus, new species. Diagnosis: Abyssianiridae with coxal plates visible in dorsal view on last three peraeonal somites only. Lateral margins of cephalon not flattened and expanded. Composition: Monotypic. Affinities: Closely related to Abyssianira but resembling the Nannoniscidae in general body shape. The peraeopods are ambulatory and none is modified for swimming; the mandibular molar is stout and truncated at the end.
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SUMMARY 83 INTRODUCTION 84 Material
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Family: Munnidae 172 A Key to the G
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In this paper the marine isopods of
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86 ROBERT J. MENZIES Hansen (1897)
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88 ROBERT J. MENZIES 90. Eurycope g
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90 ROBERT J. MRNZIES 10. Head subci
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92 two specimens (both larvae, one
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94 ROBERT J. MENZIES A KEY TO THE F
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96 ROBERT J. MENZIES 18. Medial pro
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98 ROBERT J. MENZIES Affinities: Th
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100 ROBERT J. MENZIES Figure 8. Hap
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102 ROBERT J. MENZIES Figure 10. A-
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106 ROBERT J. MENZIES and peraeonal
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ROBERT J. MENZIES Figure 14. A-B: A
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112 ROBERT J. MENZIES 6. Posterior
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120 ROBERT J. MENZIES Measurements:
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122 ROBERT J. MENZIES 1. Pleon with
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124 ROBERT J. MENZIES Figure 23. St
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126 ROBERT J. MENZIES Diagnosis: St
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Page 52 and 53: 130 Macrostylis setifer, new specie
Page 54 and 55: 132 ROBERT J. MENZIES Figure 29. A-
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Page 60 and 61: 138 ROBERT J. MENZIES Nannoniscus l
Page 68 and 69: 146 ROBERT J. MENZIES 2. Dorsum of
Page 70 and 71: 148 below these spines the lateral
Page 72 and 73: 150 ROBERT J. MENZIES Figure 39. St
Page 74 and 75: Figure 41. A-E: C: uropod; D: male.
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Page 78 and 79: 156 LIST OF ILYARACHNA SPECIES Spec
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Page 82 and 83: 160 ROBERT J. MENZIES or lateral. U
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Page 90 and 91: 168 ROBERT J. MENZIES Genus: IANIRE
Page 94 and 95: 172 ROBERT J. MENZIES Rhacura pulch
Page 96 and 97: 174 ROBERT J. MENZIES ramus small,
Page 98 and 99: 176 ROBERT J. MENZIES Figure 59. No
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Page 106 and 107: 184 ROBERT J. MENZIES Genus: THAMBE
Page 108 and 109: 186 ROBERT J. MENZIES The three sub
Page 110 and 111: 188 Uropodal rami blunt, endopod on
Page 112 and 113: 190 ROBERT J. MENZIES Figure 69. Gl
Page 114 and 115: 192 ROBERT J. MENZIES Measurements:
Page 116 and 117: 194 ROBERT J. MENZIES possible. Thi
Page 118 and 119: LIST OF ATLANTIC ABYSSAL BIOLOGICAL
Page 120 and 121: 198 ROBERT J. MENZIES Haploniscus (
Page 122 and 123: 200 ROBERT J. MENZIES Eurycope (Ind
Page 124 and 125: LIST OF OTHER ABYSSAL ATLANTIC AND
Page 126 and 127: 204 ROBERT J. MENZIES Haplomesus qu
Page 128: 206 ROBERT J. MENZIES Crustacea Iso
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The Isopods of Abyssal Depths in the Atlantic Ocean

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