The Isopods of Abyssal Depths in the Atlantic Ocean

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116 ROBERT J. MENZIES Figure 19. A-G: Ischnomesuspaucispinis, n. sp. A: uropod; B: first antenna; C: first male pleopod; D: maxilliped; E: mandible; F: dorsal view male holotype minus cephalon; G: dorsal view male paratype fragment. H-K: Ischnomesus decemspinosus, n. sp. H: dorsal view male holotype; I: second male pleopod; J: first male pleopod; K: first antenna. L-N: Ischnomesus elegans, n. sp. L: dorsal view male holotype; M: first male pleopod; N: second male pleopod. Type locality: South Atlantic, L.G.O. Biotrawl No. 12, type plus one male paratype fragment, cat. no. 1-95. Distribution: Known only from type locality. Affinities: This species is unique in having the postero-lateral angles of the pleon projecting beyond the medial distal border. Otherwise it belongs with the group of species lacking a lateral spine from the sixth peraeonal somite. Ischnomesus paucispinis, new species Figure 19 A-G Synonyms: None.
Diagnosis: Ischnomesus with lateral spines only on first peraeonal somite. Dorsal spines lacking. Pleon with stout setae on either side of pronounced posterolateral angle, three smaller setae follow, apex with two minute setae. Lateral projections at apex of male first pleopod well developed, apex each with six stout setae. Measurements: Holotype male fragment length 4.3 mm. (minus cephalon), width pleon 0.65 mm. Type locality: South Atlantic, L.G.O. Biotrawl No. 12, holotype and one male fragment, cat. no. 1-93. Distribution: Known only from type locality. Affinities: The stout setae on the lateral margin of he pleon distinguish this species from the others, as foes the fact that the fifth peraeonal somite lacks ateral spines. Ischnomesus decemspinosus, new species Figure 19 H-K Synonyms: None. Diagnosis: Ischnomesus with lateral spines on perae- :ial somites 4-5 inclusive; somites 2—4 each with a : air of dorsal spines. Pleon ovoid, smooth, devoid of :pines, setae, or sharp postero-lateral angles. Lateral D rejections at apex of first male pleopod well developed, apex of each with seven stout setae. Measurements: Male holotype length 8.4 mm., width pleon 0.9 mm. Type locality: South Atlantic, L.G.O. Biotrawl Xo. 14, type and one fragment, cat. no. 1-44. Distribution: Known only from type locality. Affinities: The fact that the dorsal surface of the fourth peraeonal somite has spines sets this species apart from the majority, plus the fact that the fifth peraeonal somite has long lateral spines. Ischnomesus elegans, new species Figure 19 L-N Synonyms: None. Diagnosis: Ischnomesus with lateral spines on peraeonal somites 2-5 inclusive. Dorsal spines lacking. Pleon with sharp postero-lateral angles at uropods, margins entire and smooth, posterior margin truncated and smooth. Lateral projection at apex of male first pleopod largely joined to sympod, distal margin without setae. Measurements: Holotype male length 10.01 mm. (minus cephalon), width pleon 1.5 mm. Type locality: South Atlantic, L.G.O. Biotrawl No. 214, type only, cat. no. 1-76. Distribution: Known only from type locality. Affinities: This species is closely related to /. bacillus (Beddard), but has the pleonal border swollen and not subparallel. ABYSSAL ATLANTIC ISOPODS 117 Ischnomesus species indeterminate Unidentifiable fragments of Ischnomesus were collected at L.G.O. Biotrawl no. 12, eleven fragments; 18, five fragments; 52, two fragments; 53, three fragments; 98, one fragment; 217, one fragment; 220, one fragment; 233, one fragment. Genus: HAPLOMESUS Richardson Synonyms: Haplomesus Richardson, 1908a, p. 81; — Hansen, 1916, p. 59; — Wolff, 1956, p. 87. Type species: Ischnosoma quadrispinosa G. O. Sars, 1879, p. 435. Diagnosis: Ischnomesidae with third article of first antennae elongate, two and a half times or more longer than the fourth. Pleon with a single somite only. Uropoda with a single article. Fifth to seventh peraeonal somites fused with pleon. Remarks: Eight species, all from the Atlantic and Pacific, are presently known from this genus: Depth Range (Meters) Species Least Greatest 1. quadrispinosus (G. O. Sars) 510 4150 2. angustus Hansen 698 2137 3. insignis Hansen 698 2707 4. tenuispinis Hansen 698 3474 5. modestus Hansen — 2258 6. brevispinis Birstein 5510 5690 7. cornutus Birstein 6471 6571 8. orientalis Birstein 4000 4150 Additionally, three new species are described in this paper from abyssal depths of the North and South Atlantic. A KEY TO THE SPECIES OF HAPLOMESUS 1. Third peraeonal somite with lateral spines ... 2 1. Third peraeonal somite without lateral spines . . 5 2. Fourth peraeonal somite with lateral spines modestus Hansen 2. Fourth peraeonal somite without lateral spines . . 3 3. Apex of pleon medially incised . . . . bifurcatus, n. sp. 3. Apex of pleon truncated or curved not medially incised 4 4. Dorsum of pleon medially with paired carinae ornatus, n. sp. 4. Dorsum of pleon medially with a single swelling quadrispinosus (G. O. Sars) 5. Fourth peraeonal somite with lateral spines ... 6 5. Fourth peraeonal somite without lateral spines . . 8 6. Dorsum of pleon with at least one pair of stout spines near midline tenuispinis Hansen 6. Dorsum of pleon without paired stout spines ... 7 7. Lateral spines of first and fourth peraeonal somites massive, longer than wide insignis Hansen 7. Lateral spines of first and fourth peraeonal somites short, no longer than wide . . tropicalis, n. sp. 8. Posterior border of pleon trilobed . . . angustus Hansen 8. Posterior border of pleon with one median lobe only gorbunovi Gurjanova" a More probably this species belongs in the genus Stylomesus.
Page 1 and 2: SUMMARY 83 INTRODUCTION 84 Material
Page 3: Family: Munnidae 172 A Key to the G
Page 6 and 7: In this paper the marine isopods of
Page 8 and 9: 86 ROBERT J. MENZIES Hansen (1897)
Page 10 and 11: 88 ROBERT J. MENZIES 90. Eurycope g
Page 12 and 13: 90 ROBERT J. MRNZIES 10. Head subci
Page 14 and 15: 92 two specimens (both larvae, one
Page 16 and 17: 94 ROBERT J. MENZIES A KEY TO THE F
Page 18 and 19: 96 ROBERT J. MENZIES 18. Medial pro
Page 20 and 21: 98 ROBERT J. MENZIES Affinities: Th
Page 22 and 23: 100 ROBERT J. MENZIES Figure 8. Hap
Page 24 and 25: 102 ROBERT J. MENZIES Figure 10. A-
Page 28 and 29: 106 ROBERT J. MENZIES and peraeonal
Page 30 and 31: ROBERT J. MENZIES Figure 14. A-B: A
Page 34 and 35: 112 ROBERT J. MENZIES 6. Posterior
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Page 44 and 45: 122 ROBERT J. MENZIES 1. Pleon with
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Page 48 and 49: 126 ROBERT J. MENZIES Diagnosis: St
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Page 52 and 53: 130 Macrostylis setifer, new specie
Page 56 and 57: 134 ROBERT J. MENZIES Figure 30. Na
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.
Page 76 and 77: 154 ROBERT J. MENZIES Figure 43. Ac
Page 78 and 79: 156 LIST OF ILYARACHNA SPECIES Spec
Page 80 and 81: 158 ROBERT J. MENZIES Figure 46. Il
Page 82 and 83: 160 ROBERT J. MENZIES or lateral. U
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166 ROBERT J. MENZIES Figure 51. A-
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168 ROBERT J. MENZIES Genus: IANIRE
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172 ROBERT J. MENZIES Rhacura pulch
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174 ROBERT J. MENZIES ramus small,
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176 ROBERT J. MENZIES Figure 59. No
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ROBERT J. MENZIES Figure 60. Acanth
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180 ROBERT J. MENZIES Figure 61. A:
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184 ROBERT J. MENZIES Genus: THAMBE
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186 ROBERT J. MENZIES The three sub
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188 Uropodal rami blunt, endopod on
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190 ROBERT J. MENZIES Figure 69. Gl
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192 ROBERT J. MENZIES Measurements:
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194 ROBERT J. MENZIES possible. Thi
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LIST OF ATLANTIC ABYSSAL BIOLOGICAL
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198 ROBERT J. MENZIES Haploniscus (
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200 ROBERT J. MENZIES Eurycope (Ind
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LIST OF OTHER ABYSSAL ATLANTIC AND
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204 ROBERT J. MENZIES Haplomesus qu
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206 ROBERT J. MENZIES Crustacea Iso
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The Isopods of Abyssal Depths in the Atlantic Ocean

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