Deep-sea Fauna and Pollutants off Pacific Coast of Northern Japan, edited by T. Fujita, National Museum of Nature andScience Monographs, No. 39, pp. 483-493, 2009

Deep-sea Cumacean Crustaceans (Peracarida) Collected from Pacific Coast of
Northern Honshu, Japan
Tadashi Akiyama
Ushimado Marine Laboratory, Okayama University, Ushimado, Okayama, 701 4303, Japan
E-mail: akiyama@uml.okayama-u.ac.jp

Abstract: Deep-sea cumaceans from the Pacific coast of Northern Honshu, Japan, 249 5367 m deep, werecollected by the R/V Soyo-maru, R/V Wakataka-maru and R/V Tansei-maru in 1992, and 2005 2007. Twentyseven species from families Bodotridae, Leuconidae, Nannastacidae, and Diastylidae were identified, among
which Platycuma japonicum was new to science.
Key words: Cumacea, Crustacea, deep-sea, Japan, Northern Pacific.

Introduction
Relatively little is known about the deep-sea cumacean fauna of the Pacific coast of northern
Japan. However, the cumacean fauna of the eastern coast of the Russia, including the Okhotsk Sea,
Kamchatka and the Sea of Japan, was well documented by Lomakina (1955, 1958). Calman (1912)
reported 10 cumacean species from shallow waters of the Bering Sea, off Alaska and Sakhalin, 7
species of which have also been reported from the sea floor deeper than 200 m (Bacescu, 1988,
1991). From Pacific coast of northern Honshu, Japan, Gamô (1985, 1987, 1988a, b, 1989, 1999)
and Harada (1962) reported 15 deep-sea cumacean species, which would comprise only a small
portion of the complete fauna of this region.
During the project “Research on Deep-sea Fauna and Pollutants off Pacific Coast of Northern
Japan” by Natural Museum of Nature and Science (NSMT), a large number of deep-sea benthic
organisms from this region were collected. The present study describes the cumacean specimensfrom the NSMT collection.
Materials and Methods
The cumacean specimens examined in this study were collected by the R/V Wakataka-maru
and R/V Soyo-maru of the Fisheries Research Agency (FRA), and the R/V Tansei-maru of theJapan Agency for Marine-Earth Science and Technology (JAMSTEC), between 2005 and 2007.
Some specimens collected by the R/V Soyo-maru in 1992 were also examined. The gears used forthe collections were biological dredges and beam trawls of 3 m span. In some collections, small
ring nets, 30 cm in diameter, 0.5 mm or 1 mm opening, were attached to the gears to catch small
animals including cumaceans. The stations where cumacean specimens examined in the present
study were collected are listed in Table 1. The specimens examined are deposited in NSMT.

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Table 1. List of the sampling sites. Abbreviations for Haul. no. and Gear: SO, R/V Soyo-maru; WA, R/V Wakataka-maru; KT,
R/V Tansei-maru; BT, beam trawl; DG, biological dredge.
Haul. no.

Date

Position in

SO92-St. 5
SO07-C7-B
SO07-K1
SO07-K2
SO07-K3
SO07-O1
SO07-O3
SO07-O4
WA05-DE250D
WA05-FG250D
WA06-DE280D
WA06-E1200D
WA06-EF425D
WA06-F1500D
WA06-G900D
WA06-H1500D
KT07-29-H1
KT07-29-H2
KT07-29-M1
KT07-29-M2
KT07-29-M3-1
KT07-29-M3-2
KT07-29-M3-3

30 Jun. 1992
5 Aug. 2007
6 Aug. 2007
6 Aug. 2007
7 Aug. 2007
8 Aug. 2007
8 Aug. 2007
7 Aug. 2007
19 Nov. 2005
14 Nov. 2005
23 Nov. 2006
2 Nov. 2006
21 Nov. 2006
1 Nov. 2006
11 Nov. 2006
15 Nov. 2006
8 Nov. 2007
8 Nov. 2007
5 Nov. 2007
5 Nov. 2007
5 Nov. 2007
6 Nov. 2007
8 Nov. 200741˚39.4´N, 142˚10.2´E
39˚40.6´N, 142˚35.2´E
38˚35.4´N, 143˚04.5´E
38˚34.7´N, 143˚32.9´E
38˚29.0´N, 143˚40.1´E
36˚46.0´N, 141˚51.4´E
36˚57.1´N, 142˚39.9´E
37˚00.6´N, 142˚57.4´E
38˚40.6´N, 141˚55.3´E
37˚19.9´N, 141˚37.7´E
38˚42.91´N, 141˚58.34´E
38˚19.25´N, 142˚31.74´E
38˚03.26´N, 142˚03.97´E
37˚34.64´N, 142˚33.47´E
36˚47.53´N, 141˚39.39´E
36˚36.45´N, 141˚36.21´E
40˚48.70´N, 142˚00.05´E
40˚00.00´N, 143˚31.37´E
39˚17.86´N, 142˚28.40´E
39˚16.20´N, 142˚41.07´E
39˚20.04´N, 142˚50.99´E
39˚20.19´N, 142˚51.40´E
39˚20.09´N, 142˚51.17´E

Position out
41˚37.7´N, 142˚10.7´E39˚39.8´N, 142˚33.7´E
38˚34.0´N, 143˚06.9´E
38˚30.6´N, 143˚35.6´E
38˚34.3´N, 143˚42.5´E
36˚43.8´N, 141˚48.1´E
36˚52.4´N, 142˚35.7´E
36˚56.3´N, 142˚58.9´E――
38˚43.12´N, 141˚58.37´E
38˚19.36´N, 142˚31.65´E
38˚03.12´N, 142˚04.25´E
37˚39.39´N, 142˚34.32´E
36˚47.32´N, 141˚39.14´E
36˚36.66´N,141˚36.14´E
40˚47.36´N, 142˚00.49´E
41˚00.76´N 143˚30.25´E
39˚16.80´N, 142˚27.37´E
39˚18.62´N, 142˚43.73´E
39˚21.75´N, 142˚51.90´E
39˚19.23´N, 142˚49.18´E
39˚19.23´N, 142˚49.05´E

Depth (m)Gear1150 1170
815 8202043 2183
2968 3032
3990 4181
2020 2068
4075 4128
5000 5367
249
253 255284 2851213 1214
420 424
1466 1511
920 9251450 1470
454 972032 2055
1039 1041
1528 1603
1719 1728
1709 1737
1733 1695

BT
BT
BT
BT
BT
BT
BT
BT
DG
DG
DG
DG
DG
DG
DG
DG
BT
BT
BT
BT
BT
BT
BT

Taxonomy
Family Lampropidae Sars, 1878
Genus Hemilamprops Sars, 1883
Hemilamprops sp.
Material examined. SO07-K3 (2♂, 1♀, 3 juv.), NSMT-Cr 19749.
Family Bodotriidae Scott, 1901
Subfamily Bodotriinae Scott, 1901
Genus Cyclaspoides Bonnier, 1896
Cyclaspoides sp.
Material examined. KT07-29-H2 (3♀, 4 juv.), NSMT-Cr 19750.
Remarks. Three known species of the genus, Cyclaspoides sarsi Bonnier, 1896, C. pellucidus
Day, 1978 and C. bacescui Petrescu, 1995, have been reported from, respectively, the deep Atlantic, 698 4934 m depth; off South Africa, 400 m depth; and from the eastern Pacific, off Ecuador,1892 m depth. The Japanese specimens are similar to C. sarsi.
Subfamily Vaunthompsoniinae Sars, 1878
Ginus Bathycuma Hansen, 1895
Bathycuma granulatum Gamô, 1989
Bathycuma granulatum Gamô, 1989: 11 17, figs. 1 3.

Deep-sea Cumacea from Northern Japan

485

Material examined. SO07-K3 (2♂, 3 juv., 3 manca), NSMT-Cr 19751; SO07-K2 (1 juv.),
NSMT-Cr 19752; SO07-O4 (1♀), NSMT-Cr 19753.
Distribution. Pacific coast of northern Honshu, 2968 6416 m depth.
Bathycuma declinatum Gamô, 1989
Bathycuma declinatum Gamô, 1989: 17 23, figs. 4 6.

Material examined. SO07-K3 (2 juv.), NSMT-Cr 19754.
Distribution. Off Kinkazan, Pacific coast of northern Honshu, 3990 6416 m.
Family Leuconidae Sars, 1878
Genus Leucon Kröyer, 1846
Subgenus Leucon Kröyer, 1846
Leucon (Leucon) armatus Given, 1961
Leucon armatus Given, 1961: 136 139, fig. 35A D.

Material examined. KT07-29-H2 (2♀, 1 juv.), NSMT-Cr 19755.
Distribution. California, Pacific eastern coast, Pacific coast of northern Honshu, 186 2055m.
Leucon (Leucon) kobjakovae Lomakina, 1955
Leucon kobjakovae Lomakina, 1955: 241 243, fig. 157.
Leucon (Leucon) kobjakovae: Bacescu, 1988: 155.

Material examined. KT07-29-H1 (40♀, 70 juv.), NSMT-Cr 19756.
Distribution. Okhotsk Sea, Kamtcatka, the Sea of Japan, Pacific coast of northern Honshu,
48 497 m.
Leucon (Leucon) sp. 1
Material examined. WA05-DE250D (15♀, 10 juv.), NSMT-Cr 19757; WA06-DE250D (2♀,
1 juv., 1 manca), NSMT-Cr 19758.
Remarks. Carapace of the specimens have a curved ridge, which is also present in Leucon(Leucon) kobjakovae and L. (L.) falcicosta Walting and MacCann, 1997 from the eastern Pacific,
90 161 m (Watling and MacCann, 1997). However, the specimens are distinguished from the lattertwo species by a more upturned pseudorostrum.
Leucon (Leucon) sp. 2
Material examined. SO07-C7-B (1♂, 24♀, 17 juv., 3 manca), NSMT-Cr 19759.
Remarks. The specimens resemble Leucon (Leucon) robustus Hansen, 1920 from the North
Atlantic, 1000 2624 m, in having a few spines on the side of the frontal lobe of carapace. However, the former is distinguished from the latter by the shape of some appendages, including antenna 1.

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Tadashi Akiyama

Subgenus Epileucon Jones, 1956
Leucon (Epileucon) tenuirostris Sars, 1887
Leucon tenuirostris Sars, 1887: 38 40, pl. 5, figs. 1 4.
Epileucon tenuirostris: Bishop, 1981: 395 397, fig. 18.
Leucon (Epileucon) tenuirostris: Bacescu, 1988: 171.

Material examined. SO07-K2 (1♀), NSMT-Cr 19760.
Distribution. North Pacific, North Atlantic, Argentina, Angola, northern Japan, 1456 4980m.
Genus Eudorella Norman, 1867
Eudorella dentata Lomakina, 1955
Eudorella dentata Lomakina, 1955: 120 122, figs. 20 22; Lomakina 1958: 226 229, fig. 145.

Material examined. KT07-29-M1 (1 juv.), NSMT-Cr 19761.
Distribution. Okhotsk Sea, Bering Sea, Kamtchatka and the Kuriles, Pacific coast of northern
Honshu, 45 1041 m.
Eudorella emarginata (Kröyer, 1846)
Leucon emaginatus Kröyer, 1846: 181, 209, 211, pl. 2, fig. 3a h.
Eudorella emarginata: Norman, 1867: 194, 197; Sars, 1900: 36, pl. 27 28.

Material examined. WA06-E1200D (4♀, 1 juv.), NSMT-Cr 19762; WA06-H1500D (1♀, 2juv.), NSMT-Cr 19763; SO07-O1 (3♂, 3♀, 8 juv.), NSMT-Cr 19764; SO07-K1 (1♂, 1♀, 11 juv.,
10 manca), NSMT-Cr 19765; KT07-29-H2 (1♂, 2♀, 34 juv., 17 manca), NSMT-Cr 19766; KT0729-M1 (9 manca), NSMT-Cr 19767; KT07-29-M2 (8♂, 9♀, 87 juv., ca. 700 manca), NSMT-Cr
19768; KT07-29-M3-2 (2♂, 1♀, 30 juv., 102 manca), NSMT-Cr 19769.
Distribution. Circum Arctic region, Alaska, Pacific coast of northern Honshu, 0 2000 m.
?Eudorella hispida Sars, 1871
Eudorella hispida Sars, 1871: 49, pl. 18 fig. 95 97; Stebbing, 1913: 79; Hansen, 1920: 23 24, pl. 1, fig. 8a.

Material examined. SO07-K1 (1♂, 1♀, 8 juv., 3 manca), NSMT-Cr 19770.
Remarks. The specimens are similar to Eudorella hispida from the Atlantic, 2 1096 m, However, a row of several stiff setae on each side of the carapace of the specimens examined in thepresent study have not been reported in the previous studies on this species.
?Eudorella pacifica Hart, 1930
Eudorella pacifica Hart, 1930: 28 30, fig. 2; Barnard and Given, 1961: 160 163; Watling and MacCann, 1997: 155 156, fig.
2.20; Hong and Park, 1999: 451 457, figs. 5 9.

Material examined. KT07-29-M1 (3♀, 13 juv.), NSMT-Cr 19771; KT07-29-M2 (1♂, 11♀,
11 juv.), NSMT-Cr 19772.
Remarks. Eudorella pacifica has been reported from both shallow and deep waters of thenortheastern and northwestern Pacific. Previous studies reported considerable intra-specificDeep-sea Cumacea from Northern Japan

487

variation (Barnard and Given, 1961; Watling and MacCann, 1997). The taxonomic status of thisspecies therefore requires further clarification. Although the specimens from northern Honshu aresimilar to this species, further research on specimens collected from other localities and depths isrequired.
Eudorella sp.
Material examined. WA-05-DE250D (2♂, 59♀, 16 juv.), NSMT-Cr 19773; WA06-DE250D(1♂, 77♀, 259 juv., 719 manca), NSMT-Cr 19774; WA06-DE280D (2♂, 394♀, 14 juv.), NSMT-Cr
19775.
Remarks. The specimens are similar to Eudorella pusilla Sars, 1871 from the North Atlantic,
2 256 m, but are distinguishable from the latter by the pointed posterior end of the last abdominal
segment.
Genus Eudorellopsis Sars, 1882
Eudorellopsis biplicata Calman, 1912
Eudorellopsis biplicata Calman, 1912: 625 626, figs. 25 26.

Material examined. WA05-DE250D (2♀, 3 juv.), NSMT-Cr 19776; WA06-DE250D (9♀, 5juv., 32 manca), NSMT-Cr 19777; WA06-DE280D (22♂, 45♀, 29 juv.), NSMT-Cr 19778.
Distribution. North Pacific and the North Atlantic, 20 1514 m.
Eudorellopsis integra (Smith, 1879)
Eudorella integra Smith, 1879: 116.
Eudorellopsis integra: Hansen, 1887: 201 203, fig. 3a d; Calman, 1912: 624; Lomakina, 1958: 209 211, fig. 127.

Material examined. KT07-29-M2 (12♂, 14♀, 25 juv., 49 manca), NSMT-Cr 19779; KT0729-M3-1 (1♂, 4♀), NSMT-Cr 19780; KT07-29-M3-2 (1♂, 2♀, 1 juv., 10 manca), NSMT-Cr
19781.
Distribution. West Atlantic, Bering Sea and Okhotsk Sea, Pacific coast of northern Honshu,
1.5 1737 m.
Remarks. Japanese specimens are characterized by well defined antero-lateral corner of thecarapace, and by a stout spine on the dorsal crest of the carapace in some specimens.
Eudorellopsis uschakovi Lomakina, 1955
Eudorellopsis uschakovii Lomakina, 1955: 129 130, figs. 27 29.

Material examined. KT07-29-M2 (1♂, 1♀, 5 juv., 5 manca), NSMT-Cr 19782; KT0729-M3-2 (3♂, 6♀, 14 manca), NSMT-Cr 19783; KT07-29-M3-3 (5♂, 8♀, 1 juv., 8 manca),
NSMT-Cr 19784.
Distribution. Okhotsk Sea, Pacific coast of northern Honshu, 85 1733 m.

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Tadashi Akiyama

Family Nannastacidae Bate, 1866
Genus Platycuma Calman, 1905
Platycuma japonicum sp. nov.
(Figs. 1 2)
Material examined. Holotype: NSMT-Cr 19785, ovigerous female, length 3.3 mm, off Kinkazan, 2043 2183 m, 38˚33.2´N, 143˚4.1´E 38˚34.0´N, 143˚6.9´E, 6 August, 2007 (SO07-K1). Paratypes: NSMT-Cr 19786, 1 preparatory female (dissected, length 3.4 mm), 7 juveniles, length
2.4 2.7 mm, off Miyako, 1700 1733 m, 39˚20.1´N, 142˚51.2´E 39˚19.2´N, 142˚49.1´E (KT0729-M3-3).
Description. Females (no males observed). Body (Figs. 1A, 2A) white, weakly calcified, withfew hairs. Carapace (Figs. 1A B, 2A B) very smooth, length 0.4 times total length of body, and aslong as width, which is 1.5 times dorsoventral depth. Eye lobe very small; antennal notch shallow,
with a tooth at the lower end. Carapace with 4 teeth on anterior portion of lower margin. Side ofcarapace elongated posteriorly, covering 1st and 2nd pleonite.
Pereon (Figs. 1A B, 2A B) very short, 5th segment with 2 serrated dorsal keels. Pleon (Figs.
1A, 2A) slightly shorter than half of total body length; 1 5th segments with 2 rows of dorsal keels
pointed posteriorly; 2 4th segments subequal in length each other, shorter than the 5th; last segment not protruding between uropods (Fig. 1P).
Antenna 1 (Fig. 1C) with 2 long simple setae on peduncle. First segment of peduncle longer
than 2nd, which is slightly longer than 3rd; 3-segmented main flagellum shorter than 3rd segmentof peduncle; accessory flagellum minute. Antenna 2 (Fig. 1D) with 3 plumose setae on distal margin. Labium (Fig. 1E) with 4 teeth on distal margin. Right mandible (Fig.1F) boat shaped, with 7
plumose setae on inner border. Maxilla 1 (Fig. 1G) with 2 filaments on palp. Maxilla 2 (Fig. 1H)
normal. Maxilliped 1 (Fig. 1I) with 2 branchial lobules. Maxilliped 2 (Fig. 1J). Basis broad, slightly shorter than distal segments combined, with 2 plumose setae on distal end; carpus and propodus
each with 3 simple setae on inner border. Maxilliped 3 (Fig. 1K). Basis slightly shorter than the
distal segments combined, and with 6 plumose setae on distal end; propodus curved, with 3 simple
setae on inner border.
Pereopod 1 (Fig. 1L). Basis 0.8 times the distal segments together, almost naked on inner andouter border; carpus subequal in length to propodus and twice as long as dactylus. Pereopod 2 (Fig.
1M). Basis as long as distal segments combined; dactylus much longer than carpus. Pereopod 3(Fig. 1N). Basis slightly shorter than distal segments together; carpus 2.5 times as long as merus.
Pereopod 4 (Fig. 1O). Basis 0.8 times as long as distal segments combined; carpus elongated, 3.4
times as long as merus, 0.7 times as long as basis. Pereopod 5 absent.
Uropod (Fig. 1P) as long as combined length of last 3 pleonites. Peduncle 2.2 times the lastpleonite and 1.8 times as long as exopod, with 4 minute setae on inner border; exopod subequal inlength to uni-articulated endopod, with 1 simple seta on the inner border and 2 simple setae on
distal end; dorsal surface of exopod with a simple seta. Single segmented endopod with 4 robust
setae on distal end and with several auditory hairs on dorsal surface.
Etymology. The species name refers to the Japanese type locality.
Remarks. All 5 known species of the genus, Platycuma holti, P. marginata, P. sandersi, P.
hessleri, and P. candida, have been hitherto reported from deep waters in the Atlantic (Calman,
1905; Zimmer, 1943, 1980; Jones, 1973, 1984). In the present new species, the shape of the carapace, with its lateral surface elongated posteriorly, and the absence of a 5th pereopod, are uniquein the genus. Platycuma japonicum is similar to P. sandersi in the dorsal keels of the abdomen andthe shape of the appendages, but is distinguished from the latter by the characters mentioned
above. The genus Platycuma is mostly characterized by a coiled anterior gut. In the ovigerous

Deep-sea Cumacea from Northern Japan

Fig. 1. Platycuma japonicum sp. nov. A B, holotype ovigerous female (length 3.3 mm; NSMT-Cr 19785); C P,
paratype preparatory female (length 3.4 mm; NSMT-Cr 19786). A, habitus, lateral view; B, anterior portion ofbody, dorsal view; C, antenna 1; D, antenna 2; E, right mandible; F, maxilla 1; G, maxilla 2; H, laburum; I K,
maxillipeds 1 3; L O, pereopods 1 4; P, uropod with last abdominal segment.

489

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Tadashi Akiyama

Fig. 2. Platycuma japonicum sp. nov. A B, paratype preparatory female (length 3.4 mm; NSMT-Cr 19786); C,
paratype juvenile (length 2.4 mm; NSMT-Cr 19786). A, habitus, lateral view; B, anterior portion of body,dorsal view; C, 5th pleonite with rudimentary pereopods 5, lateral view.

female, the large marsupium has compressed the gut region so that the alignment of the gut is noteasily observable, but the preparatory female (Fig. 2A B) shows a clearly coiled gut. Among thematerials, a juvenile specimen has rudimentary 5th pereopods (Fig. 2C).
Family Diastylidae Bate, 1856
Genus Diastylis Say, 1818
Diastyis bidentata Calman, 1912
Diastylis bidentata Calman, 1912: 637 640, figs. 45 49.

Material examined. WA05-DE250D (23♀, 9 juv), NSMT-Cr 19787; WA06-DE250D (1♀),
NSMT-Cr 19788; WA06-DE280D (1♂, 15♀, 45 juv.), NSMT-Cr 19789; WA06-EF425D (2♀),
NSMT-Cr 19790.
Distribution. Alaska, Okhotsk Sea, the Sea of Japan, Bering Sea, Pacific coast of northern
Honshu, 4 1000 m.
Diastylis ornata Lomakina, 1952
Diastylis ornata Lomakina, 1952: 167 168, figs. 21 22; Lomakina, 1958: 138 140, fig. 78.

Material examined. WA05-DE250D (2♀, 3 juv.), NSMT-Cr 19791; WA05-FG250D (1 juv.),
NSMT-Cr 19792; WA06-DE280D (1♀), NSMT-Cr 19793.

Deep-sea Cumacea from Northern Japan

491

Distribution. Okhotsk Sea, Pacific coast of northern Honshu, 83 285 m.
Diastylis samurai Zimmer, 1943
Diastylis samuraii, Zimmer, 1943: 133, figs. 1 3; Gamô, 1968: 149 150, Fig. 22.

Material examined. SO92-st. 5 (1♂, 7♀, 4 juv.), NSMT-Cr 19794; WA06-F1500D (1♂, 2♀),
NSMT-Cr 19795; WA06-H1500D (2♀), NSMT-Cr 19796.
Distribution. Off Hokkaido, Pacific coast of northern Japan, 320 1511 m.
Diastylis sp.
Material examined. SO92-st. 5 (8♀, 1♂, 9 juv.), NSMT-Cr 19797; SO07-C7-B (2 juv., 4
manca), NSMT-Cr 19798; SO07-K1 (1 juv., 4 manca), NSMT-Cr 19799.
Remarks. This species is related to Diastylis ornata in having an integument with numerous
spinules and 2-segmented uropod endopod, but is distinguished from the latter in lacking a row ofstout spines on the side of the carapace.
Genus Makrokylindrus Stebbing, 1912
Subgenus Makrokylindrus Stebbing 1912
Makrokylindrus (Makrokylindrus) omorii (Gamô, 1968)
Diastylis omorii Gamô, 1968:157 161, figs. 26 27.
Makrokylindrus (Makrokylindrus) omorii: Bacescu, 1991: 352.

Material examined.WA06-F1500D (7♀, 1 juv.), NSMT-Cr 19800; WA06-G900D (2♀),
NSMT-Cr 19801; SO07-K3 (1♀, 1♂, 2 manca), NSMT-Cr 19802.
Distribution.Sagami Bay, Pacifc coast of northern Honshu, about 920 4181 m.
Makrokylindrus (Makrokylindrus) utinomii (Gamô, 1968)
Diastylis utinomii Gamô, 1968: 163 170, figs. 29 32.
Makrokylindrus (Makrokylindrus) utinomii: Bacescu, 1991: 352 353.

Material examined. SO07-K2 (1♂, 8 juv.), NSMT-Cr 19803; SO07-K3 (2 juv., 4 manca),
NSMT-Cr 19804; SO07-O3 (3 manca), NSMT-Cr 19805.
Distribution.Sagami Bay, Pacific coast of northern Honshu, 1000 4128 m.
Genus Diastyloides Smith, 1900
?Diastyloides sp.
Material examined. WA05-DE250D (2♂, 13♀), NSMT-Cr 19806.
Remarks. The female specimens agree with the characteristics of the genus Diastyloides.
However, the absence of pleopods in males, and mandibles which are narrow at the base, are in
disagreement with the diagnosis of the genus (Sars, 1900).

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Tadashi Akiyama

Genus Leptostylis Sars, 1869
Leptostylis sp.
Material examined. SO07-K2 (10♀, 4♂), NSMT-Cr 19807.
Genus Brachydiastylis Stebbing, 1912
Brachydiastylis resima (Kröyer, 1846)
Diastylis resima Kröyer, 1846: 165 170, pl. 2, fig. 2.
Diastylopsis resima: Stebbing, 1893: 311; Sars, 1900: 65 67, pl. 47; Calman, 1912: 666.
Brachydiastylis resimus: Stebbing, 1913: 107 108, figs. 62 65.
Brachydiastylis resima: Hansen, 1920: 69; Lomakina, 1958: 162 164, Fig. 95.

Material examined. KT07-29-M2 (1♀, 2 juv., 3 manca), NSMT-Cr 19808; KT07-29-M3-2 (9manca), NSMT-Cr 19809; KT07-29-M3-3 (1♀, 2 juv., 2 manca), NSMT-Cr 19810.
Distribution. Arctic, Pacific coast of Northern Honshu, 6 1733 m.
Remarks. Japanese specimens are characterized by the presence of 1 prominent tooth on theantero-lateral corner of the carapace, and a pair of stout spines projecting backward at the posterior end of pereonite 5.
Acknowledgements
I thank the captains and crews of the R/V Wakataka-maru, R/V Soyo-maru, and R/V Tanseimaru for their help in many ways. I also thank Drs. T. Kubodera, H. Komatsu, H. Saito, T. Fujita,
K. Hasegawa, and other staff members of the Natural Museum of Nature and Science, for theircooperation in sampling. Thanks are due to Dr. S. Kojima, Director of the R/V Tansei-maru cruise(KT-07-29), for facilitating this work.
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