Holotype ZSM 20040057, Sagami Bay, 600 m, coll. Doflein 1904/05; previously unidentified museum material: BMNH 1921.10.26.5, Misaki, Sagami Bay, 333 fms (609 m), coll. A.V. Insole, May 1921; UMUTZ-CnidG-21, Gokeba, Sagami Bay, 150–20 hiro (227–29 m), coll. K. Aoki, 18 June 1902; UMUTZ-CnidG-28, Kahiwajima Is., Tosa, Kochi Prefecture, coll. K. Kinoshita, June 1909; UMUTZ-CnidG-29, same data as UMUTZ-CnidG-28; UMUTZ-CnidG-30, same data as UMUTZ-CnidG-28; UMUTZ-CnidG-33, same data as UMUTZ-CnidG-28; UMUTZ-CnidG-101, St.5, 170 fms (possibly Japanese fms) (243–257 m), coll. I. Ijima, 2 April 1895; UMUTZ-CnidG-232, same data as UMUTZ-CnidG-28; RMNH Coel. 41900 (AKM 430), Zeni-su, off Izu Islands, 33°53'N 138°43'E, R/V Tansei-maru, KT04-06, st. ZN-3, 267.3–288.3 m, coll. A.K. Matsumoto, 3 April 2004; RMNH Coel. 41901 (AKM 571), Otsuki, Tosa, Kochi Prefecture, 32°43'N, 132°48'E, local fishermen’s boat, Kiryo-maru, st. 3, coral-net, 84.75–83.1 m, coll. A.K. Matsumoto, 7 October 2004; ?BMNH 1921.10.26.24-2, Misaki, Sagami Bay, 500–600 fms (715-1097 m), coll. A.V. Insole No. 45.

Colony branched in one plane with few anastomoses (Fig. 1a). Points with slightly bent spindles up to 0.17 mm long, distal end with more developed tubercles (Fig. 2a). Collaret with bent spindles up to 0.30 mm long, middle part with more developed tubercles (Fig. 2b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 2c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 2d). Coenenchyme with predominantly capstans (Fig. 3a), double disks (Fig. 3b) and disk spindles (Fig. 3c), 0.05–0.10 mm long, and small clubs of similar length (Figure 2e). Spindles, 0.10–0.20 mm long, with simple tubercles, are also present (Fig. 3d); some sclerites are intermediate between clubs and spindles (Fig. 3e). The calyces with additional clubs, up to 0.14 mm long (Fig. 2f).

Colony white, sclerites colorless.

RMNH Coel. 41900, UMUTZ-CnidG-28 (Fig. 1d), UMUTZ-CnidG-30, UMUTZ-CnidG-33, RMNH Coel. 41900 and BMNH 1921.10.26.24-2 are yellow with yellow sclerites; UMUTZ-CnidG-21, UMUTZ-CnidG-101 and UMUTZ-CnidG-232 are orange colonies; UMUTZ-CnidG-29 is red. RMNH Coel. 41901 is orange with red polyps (Fig. 1b), polyp sclerites pink, all others yellow. The sclerites of RMNH Coel. 41901 are similar to the holotype (Figs 4, 5) but it has somewhat longer coenenchymal spindles, up to 0.25 mm long (Fig. 5d).

Melithaea abyssicola occurs in Sagami Bay, off the Izu Islands, and Tosa (Kochi Prefecture)(Fig. 8).

Kükenthal (1909) probably made this a variety of Acabaria modesta Kükenthal, 1908 because the colonies and sclerites of these two species have the same color. However, morphologically the sclerites of these two species are completely different by M. modesta lacking clubs, double disks and disk spindles.

The species resembles Melithaea sagamiensis sp. n., but differs in having much smaller double disks, up to 0.05 mm long.

We have tentatively included BMNH 1921.10.26.24-2 (Fig. 1c) in Melithaea abyssicola as it was collected together with BMNH 1921.10.26.5 by the same collector at the same locality, only at different depths. However, the specimen has clubs and disk spindles but lacks the double disks and shows sclerite damage caused by formalin (Figs 6, 7).

Holotype ZMH C3305, Sagami Bay (collection number in Kükenthal (1908) incorrect as 63305), coll. A. Austin.

Colony bushy (Fig. 9a). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 10a). These platelets are up to 0.10 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 10b). Coenenchyme with capstans (Fig. 10c), about 0.05 mm long, the bigger ones are spheroids (Fig. 10d); small clubs of similar length; spindles, 0.10–0.30 mm long, with simple or complex tubercles (Figs 10e, 11). The axis has smooth and sparsely tuberculate rods (Fig. 10f).

Red with paler polyps, sclerites orange, tentacle sclerites colorless.

The name of collector A. Austin could actually be Alan Owston (Isono 1988), an English trader (import and export merchant and naturalist), who used to collect material of deep-water species. Therefore we suspect M. arborea to grow in deeper water. So far it is only found in Sagami Bay (Fig. 8).

The colony depicted by Kükenthal (1908) could actually be the basal part of a much larger colony. As with M. japonica, many sclerites are disintegrated, and therefore we could not depict the small clubs of the coenenchyme. Also, the sample available to us had hardly any polyp sclerites, since only a few tentacle rods were present (Fig. 10a). Therefore, we assume that they also had disintegrated. Kükenthal (1908) described collaret and point sclerites as being 0.20 mm long, the tentacle rods 0.15 mm long. He did not mention the presence of capstans and small clubs. We found no sclerites resembling clubs referable to calyces and only a few sclerites with a tendency to be unilaterally spinose.

According to Kükenthal (1908) the species resembles mostly M. japonica. Indeed the sclerites of these two species are very similar, M. japonica showed somewhat more developed unilaterally spinose sclerites and some sclerites resembling clubs. Bearing in mind the colony fragment of M. arborea resembles a basal part we do not exclude the possibility M. arborea and M. japonica represent one and the same species. Therefore, they were given the same position in the key to species identification.

Holotype UMUTZ-CnidG-205, Ogasawara Isls. (= Bonin Isls.), Japan, coll. S. Hirota and Sekiguchi, 11 April 1894; paratype UMUTZ-CnidG-255, same data as holotype.

The holotype is 8 cm long and 4.5 cm wide, branching is in two parallel planes, and with a holdfast (Fig. 9b). The stem is 5 mm wide, the end branches only 1 mm wide. The colony has many anastomoses. The polyps are situated all around the branches, the calyces are dome-shaped, and the polyps are retracted. Points with slightly bent spindles up to 0.15 mm long, distal end with leaves (Fig. 12a). Collaret with bent spindles up to 0.20 mm long, middle part with more tubercles or side branches (Fig. 12b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 12c). These platelets are up to 0.10 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 12d). Coenenchyme with capstans (Fig. 12e), unilaterally foliate spheroids (Fig. 12f), 0.05–0.10 mm long and small clubs of similar length (Fig. 12g); spindles (Fig. 13b) and unilaterally foliate spindles (Fig. 13a) are 0.10–0.20 mm long. The calyces with longer clubs, up to 0.15 mm long (Fig. 12h). Most coenenchymal sclerites have complex tubercles.

The colony and sclerites are orange.

The species is only known from the Ogasawara Islands (= Bonin Islands) (Fig. 8).

Etymology. The species is named after the type locality, the Bonin Islands.

This is the first record of Melithaea from this island group. The colony shape of paratype UMUTZ-CnidG-255, collected at the same time with G205, looks similar toZ-CnidG-205, but it has disintegrated sclerites. The colony is slightly smaller and brighter orange-colored (Fig. 9c). Its sclerites are similar to those of the holotype. This is the only species that looks like M. habereri (Kükenthal, 1908), having many anastomoses, but its sclerites are quite different, many with leaves, while Kükenthal described spiny sclerites for M. habereri.

Syntype ZMB 5814, Misaki (Japan), coll. Doflein, 1904/05; previously unidentified museum material: ZMUC ANT-000587, Okinose, Sagami Bay, Japan, 100 fms (143–183 m), coll. Dr. Th. Mortensen, 26 June 1914; ZMUC ANT-000588; Sagami Bay, Japan, 80–120 fms (114–219 m), coll. Dr. Th. Mortensen, 6–19 June 1914; ZMUC ANT-000590, Okinose, Sagami Sea, 100 fms (143–183 m), coll. Dr. Th. Mortensen, 15 June 1914; ZMUC ANT-000646, Off Nagasaki, 32°15'N, 128°12'E, 90 fms (165 m), coll. Dr. Th. Mortensen, 15 May 1914; ZMUC ANT-000654, Okinose, Sagami Sea, 100 fms (143–183 m),, coll. Dr. Th. Mortensen, 23 June 1914; ZMUC ANT-000659, Okinose, Sagami Bay, 200 fms (286–366 m), coll. Dr. Th. Mortensen, 1 July 1914; ZMUC ANT-000661, same data as ZMUC ANT-000654; ZMUC ANT-000650, Off Misaki, Sagami Bay, ca.250 fms (ca.358–457 m), coll. Dr. Th. Mortensen, 10 June 1914; UMUTZ-CnidG-15, Japan; UMUTZ-CnidG-17, Gorgonian cave at Koajiro, Misaki, Sagami Bay, 16 July 1897; UMUTZ-CnidG-23 (G-23a), same data as UMUTZ-CnidG-17; UMUTZ-CnidG-268 (G-37d), Misaki, Sagami Bay, coll. K. Kinoshita, summer 1906; UMUTZ-CnidG-41, Awa Kominato, Boso Peninsula, Chiba Prefecture, coll. sp. no. 78, April 1885; UMUTZ-CnidG-271 (G-41b), same data as UMUTZ-CnidG-41; UMUTZ-CnidG-199, Sengenzuka-Aoyamadashi line, Sagami Bay, 100 hiro (143–151 m), coll. H. Matsumoto and H. Chiba, 20 July 1913; RMNH Coel. 41902 (AKM 223), South of Mera-se bank, Sagami Bay, 34°59.6'N, 139°41.1'E - 34°59.7'N, 139°41.1'E, 81–78 m, R/V Shinyo-maru, St.1, coll. A.K. Matsumoto, 17 October 2003; AKM 225, same data as RMNH Coel.41902; AKM 242, South of Mera-se Minami knoll, 34°54.8'N, 139°39.7'E - 34°54.8'N, 139°39.9'E, 348–312 m, R/V Shinyo-maru, coll. A.K. Matsumoto, 18 October 2003; AKM 245, South of Mera-se bank, Sagami Bay, 34°54N 139°39E, 315-365m, R/V Shinyo-maru, coll. A.K. Matsumoto, 18 October 2003; AKM 246, South of Mera-se Minami knoll, 34°54.2'N, 139°39.9'E - 34°54.3'N, 139°39.3'E, 348–312 m, R/V Shinyo-maru, coll. A.K. Matsumoto, 18 October 2003; AKM 248, same data as AKM245; AKM 253, Sagami Bay, 33°26.3'N, 139°42.3'E - 33°26.5'N, 139°42.0'E, 157–172 m, R/V Shinyo-maru, K-32, St. 18, coll. A.K. Matsumoto, 21 October 2003; AKM 299, Sagami Sea, 33°27'N, 139°42'E, 200–211 m, R/V Shinyo-maru, coll. A.K. Matsumoto, 21 October 2003; RMNH Coel. 41903 (AKM 513), Otsuki, Tosa, Kochi Prefecture, 132°50.44'E 32°37.66'N, - 132°47.88'E 32°37.56'N, 114 m, local fishermen’s boat, Kiryo-maru, st.1, coral net, coll. A.K. Matsumoto, 7 October 2004; AKM 578, off Ohakozaki cape, Otsuchi, Iwate Prefecture, 39°21.338N 142°00.721E, 75 m, R/V Yayoi, St. 2.3.4, coll. A.K. Matsumoto, 22 February 2005; AKM 595, entrance of Otsuchi Bay, Otsuchi, Iwate Prefecture, 39°21.858N 141°59.972E, 65.6 m, R/V Yayoi, St.1, coll. A.K. Matsumoto, 12 September 2005; RMNH Coel. 41904 (AKM 840b), East of Jogashima Spur, 35°03.52'N, 139°37.43'E - 35°04.17'N, 139°37.52'E, 397–286 m, R/V Tansei-maru, KT07-31, st. 8, coll. A.K. Matsumoto, 25 November 2007; RMNH Coel. 41905 (AKM 886), Hachijo Is., Izu Isls., 33°20.9082'N, 139°41.1841'E – 33°21.0775'N, 139°40.4931'E, 213–185 m, R/V Tansei-maru, KT07-31 (Kuramochi leg.), St.14 (L-7-200), Chain Bag Dredge, coll. A.K. Matsumoto, 26 November 2007; RMNH Coel. 41906 (AKM 928), Hachijo Is., Izu Isls., 33°22.5320'N, 139°40.492'E – 33°22.3111'N, 139°40.2511'E, 202–145 m, R/V Tansei-maru, KT07-31, St.15 (L-7-100), Chain Bag Dredge, coll. A.K. Matsumoto, 26 November 2007; RMNH Coel. 41907 (AKM 949), Toshima Is., Izu Isls., 34°33.1102'N, 139°17.4102'E – 34°33.6524'N, 139°17.6725'E, 143 m, R/V Tansei-maru, KT07-31, Kuramochi leg., St.22 (L-3-100), Chain Bag Dredge, coll. A.K. Matsumoto, 27 November 2007; RMNH Coel. 41908 (AKM 1175), off Kerama Is. Okinawa Prefecture, East China Sea, 127°27.70'E – 127°27.95'E, 26°04.59'N, – 26°04.56'N, 160–153 m, R/V Tansei-maru, KT08-33 cruise, St. KR-07, Chain Bag Dredge, coll. A.K. Matsumoto, 16 December 2008; RMNH Coel. 41909 (AKM 1176), same data as AKM 1175; RMNH Coel. 41910 (AKM 1320), off Kerama Islands. Okinawa Prefecture, East China Sea, 26°00'N, 127°12'E, 100–97 m, R/V Tanisei-maru, KT08-33, st. KR-3, coll. A.K. Matsumoto, 18 December 2008; RMNH Coel. 41911 (AKM 1321), same data as AKM 1320; AKM 1519, off Funakoshi Bay, Iwate Prefecture, 101 m, R/V Yayoi, St. 2-5, CO N, coll. A.K. Matsumoto, 26 April 2010; AKM 1525, off Oshima Is. Entrance of Otsuchi Bay and Funakoshi Bay, Iwate Prefecture, 39°22.085'N, 142°01.152'E, 97 m, by R/V Yayoi, 1 m biological dredge. coll. A.K. Matsumoto, 26 April 2010; AKM 1545, off Ohako-zaki Cape, Otsuchi, Iwate Prefecture, 86.5 m, R/V Yayoi, st. 2-2, coll. A.K. Matsumoto, 27 April 2010; RMNH Coel. 41912 (AKM 1602), South East off Taito-saki, Boso Peninsula, 35°09.31'N, 140°48.57'E – 35°09.60'N, 140°49.40'E, 311–325 m, R/V Tansei-maru, KT95-05, st. TB14, coll. S. Ohta, 26 April 1995; RMNH Coel. 41913 (AKM 1603), Okinoyama Basin, Sagami Bay, 86–88 m, R/V Tansei-maru, KT87-19, st. OKI, 1 m ORI biological dredge, coll. S. Ohta, 10 December 1987.

Colony bushy with anastomoses; end branches flattened (Fig. 14a). Points with slightly bent spindles up to 0.20 mm long, distal end with spines (Fig. 15a). Collaret with bent spindles up to 0.25 mm long, middle part with more tubercles (Fig. 15b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 15c). These platelets are up to 0.17 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 15d). Coenenchyme with predominantly spindles, 0.10-0.18 mm long (Fig. 16b), with simple or complex tubercles. A few capstans and unilaterally spinose spindles also present (Fig. 13f). Calyces with thorn clubs, 0.10-0.12 mm long (Fig. 16a).

Colony red with yellow tentacles; tentacle and pharynx sclerites colorless, all others pink.

ZMUC ANT-000587 (Fig. 14b) has a different colony shape than the syntype but the same locality, color and sclerites (Figs 17, 18). The species shows much color variation, RMNH Coel. 41902 has colorless and pink coenenchymal sclerites and yellow polyp ones. RMNH Coel. 41907 has orange coenenchymal sclerites and pink polyp ones. ZMUC ANT-000654 has colorless and pink coenenchymal sclerites, orange collaret and point sclerites and yellow tentacle ones; RMNH Coel. 41904 and RMNH Coel. 41905 show orange coenenchymal sclerites and colorless polyp ones; ZMUC ANT-000646 has a mixture of yellow and orange sclerites in both coenenchyme and polyps; RMNH Coel. 41906 is yellow with yellow sclerites. RMNH Coel. 41912 has an unique color pattern in M. corymbosa, red colony with white axis. Its sclerites are also slightly different, the polyp sclerites are less tuberculate, clubs of calyces are smaller, longer ones being very scarce, and the unilaterally spinose spindles are less developed (Fig. 19). This is probably due to the preservation in formalin. RMNH Coel. 41913 has extremely well developed unilaterally spinose spindles (Fig. 20).

Pacific coast of Japan; Sagami Bay; Izu Isls.; Boso Peninsula (Chiba Prefecture); Otsuchi (Sanriku, Iwate Prefecture); Otsuki (Tosa, Kochi Prefecture); and East China Sea; off Nagasaki; off Kerama Is.(Fig. 27).

The other syntype is in Hamburg, ZMH C3299.

We included a number of specimens in M. corymbosa, which show differences from the description above. Because of the limited material and rather small differences we refrain from describing them as new species. The specimens differ as follows: RMNH Coel. 41903 has a red colony color with white polyps (Fig. 14c), all coenenchymal sclerites are colorless, the axis sclerites are pink. It differs from M. corymbosa in having more capstans and derivatives of capstans (Figs 21, 22). RMNH Coel. 41908 (Fig. 14d) and RMNH Coel. 41909 are white colonies with colorless sclerites. They differ from M. corymbosa in having many small clubs with rounded heads (Figs 23, 24). RMNH Coel. 41910 and RMNH Coel. 41911 (Fig. 14e) have more unilaterally spinose spindles than normal for M. corymbosa (Figs 25, 26). Both colonies come from the same locality but have different color patterns. RMNH Coel. 41910 is orange with white calyces and polyps; sclerites of polyps and calyces colorless, others orange; RMNH Coel. 41911 is red with orange sclerites. ZMUC ANT-000646 has an orange colony with white polyps, sclerites yellow with colorless polyp sclerites. It differs from M. corymbosa in having more capstans and derivatives of capstans. In this respect it resembles RMNH Coel. 41903, from which it differs in having overall more tuberculate sclerites.

Holotype MZS-Cni61, Sagami Bay, 60-100 fms (143-183 m), coll. Doederlein, 1882.

Colony broken up, consisting of four fragments (Fig. 28a). Points with slightly bent spindles up to 0.25 mm long, distal end with leaves (Fig. 29a). Collaret with bent spindles up to 0.30 mm long, middle part with more developed tubercles (Fig. 29b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 29c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 29d). Coenenchyme with predominantly capstans (Fig. 30a), and small clubs resembling flower buds (Fig. 30b), up to 0.10 mm long. Spindles, 0.10-0.20 mm long, with simple tubercles, are also present. (Fig. 30c). The calyces with additional clubs, up to 0.15 mm long (Fig. 30d).

Colony fragments red, polyp sclerites light yellow, all others orange.

Sagami Bay (Fig. 35).

The species is named after the collector, Ludwig H.P. Döderlein.

The coenenchymal clubs of this species look like flower buds, similar to those described for Melitaea retifera Lamarck, 1916 by Ofwegen et al. (2000), but that species has unilaterally foliate spheroids, a type of sclerite not present in the present material.

Syntypes UPSZTY 2164 (old number UUZM 67), Hirudo Strait (= Hirado Strait), Nagasaki, Japan, 33°10'N, 129°18'E, coll. Kapt. Suenson.

Colonies branched in parallel planes, no anastomoses (Fig. 28b). End branches with bilateral polyp arrangement. Points with slightly bent spindles up to 0.30 mm long, distal end with more developed tubercles (Fig. 31a). Collaret with bent spindles up to 0.30 mm long, middle part with more developed tubercles (Fig. 31b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 31c). These platelets are up to 0.20 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 31d). Coenenchyme with capstans (Fig. 32a), unilaterally spinose spheroids (Fig. 32b) 0.05–0.10 mm long; small clubs of similar length (Fig. 32c); spindles 0.10–0.20 mm long (Fig. 32d). The calyces with longer clubs, up to 0.14 mm long (Fig. 32e). Most sclerites have complex tubercles. The axis has smooth and sparsely tuberculate rods (Fig. 31f).

White with colorless sclerites.

Only known from Hirado Strait, Nagasaki, East China Sea (Fig. 35).

The clubs and spinose spheroids with very spiny heads are characteristic for the species.

None, according to Kükenthal (1908) the material was deposited in München but it was not found there.

- after Kükenthal (1908): Colony branched in parallel planes, many anastomoses. Points and collaret sclerites 0.18 mm long, point sclerites are spiny clubs. Colony with spindles, in the calyx 0.15-0.18 mm long, in the coenenchyme about 0.18 mm long.

Yellowish orange.

According to Kükenthal (1908) this species mostly resembles M. undulata. From the description it most resembles M. corymbosa. One other Japanese melithaeid shows many anastomoses, namely M. boninensis sp. n. For differences see our discussion on that species.

Holotype UMUTZ-CnidG-34, Coral Reef, Cape Chinen, Okinawa Prefecture, Japan, 15 April 1901; paratype UMUTZ-CnidG-256, same data as holotype.

The holotype is 12 cm long and 11 cm wide, branching is in one plane and a holdfast is lacking (Fig. 28c). The stem is 10 mm wide, the end branches only 2 mm wide. The colony has no anastomoses. The polyps are situated biserially on the branches, the calyces are dome-shaped, and the polyps retracted.

Points with slightly bent spindles up to 0.20 mm long, distal end with leaves (Fig. 33a). Collaret with bent spindles up to 0.20 mm long, middle part with more developed tubercles (Fig. 33b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 33c). These platelets are up to 0.10 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 33d). Coenenchyme with capstans (Fig. 34a), and unilaterally spinose spheroids, 0.05–0.10 mm long (Fig. 34b). Furthermore spindles are present, 0.10–0.25 mm long (Fig. 34c). All with simple and complex tubercles. The calyces with additional leaf clubs, up to 0.20 mm long (Fig. 33f). The axis has smooth and sparsely tuberculate rods (Fig. 33e).

The colony is orange as are most sclerites; a few are yellow colored.

Only known from Okinawa Prefecture (Fig. 35). The material is probably collected during the Ryukyu (= Okinawa) expedition by K. Mitsukuri and I. Ikeda, in April, 1901.

The species is named after the late Prof. Naohide Isono who has worked on Japanese zoological history from the Edo to Meiji period, in appreciation of informing the first author about the collectors data in this publication.

The species resembles M. japonica but differs in having leaf clubs in the calyces. It resembles M. tenuis regarding the unilaterally spinose spheroids, but it has longer spindles in the coenenchyme. It could be Acabaria sp. A. of Aguilar-Hurtado et al. (2012), but in that case we must accept that these authors did not illustrate the remarkable unilaterally spinose spheroids that we found among the sclerites. The “spines” of these spheroids are very rounded, hardly resembling spines. However, a more appropriate term than spinose spheroids is not available (Bayer et al. 1983). Moreover, all colonies of Aguilar-Hurtado et al. (2012) had anastomoses while M. isonoi has none.

Holotype of Mopsella japonica BMNH 1946.1.14.207 dried sclerites of the type MCZ 4265, now MCZ Invertebrate Zoology ALCY-412 (microscopic slide only), Simoda (= Shimoda), Japan, coll. Prof. Hickson; NHMW 8046 (A.N. 1156), Nagasaki, Japan, I. Erber in Wien (Dr. A. v. Roretz) (possibly collected between ca.1875–1879); NHMW 8047, Enoshima, Japan, coll. Dr. Richard. v. Drasche; NHMW 12690 (A.N. 4837), Enoshima, Japan, Baron Eug. V. Ransonnet, Ostasiatisches Ex. (1873); Pleurocoralloides formosum, ZSM 20051735, type, Japan, Sagami Bay, leg. Haberer, 1901; Melitodes flabellifera: ZMB 5822, syntype, Japan, up to 20 m depth, coll. Doflein, 1904/05; NHMW 2426, Enoshima, Nagoya, coll. Drasche, Koerbl, 18–19 December 1877; MZS-Cni52, Sagami Bay, coll. Doederlein, 1882; BMNH 1936.7.6.7, Sagami Channel, Sagami Bay, purchased of Shibayama Nat. Sci. Laboratory Cat. No. 7c-7A, 7 August 1931; Melitodes densa: ZMB 5801, syntype, Sagami Bay, 60–250 m?, coll. Doflein 1904/05; ZMB 5809, syntype, Sagami Bay, littoral, coll. Doflein1904/05; previously unidentified museum material: BMNH 1883.8.29.10, Enoshima, Japan, coll. Res. by D?.F.J. Burge; MZS-Cni 235, Jogashima, Sagami Bay, Japan, coll. Doederlein; ZMUC ANT-000591, Misaki, Sagami Bay, Japan, 1–2 fms (2–4 m), coll. Dr. Th. Mortensen, 24 June 1914; UMUTZ-CnidG- 257 (G-23b), gorgonia cave at Koajiro, Misaki, Sagami Bay, 16 July 1897; UMUTZ-CnidG-258 (G-23c), same data as UMUTZ-CnidG-257 (G-23b); UMUTZ-CnidG-259 (G-23d), same data as UMUTZ-CnidG-257 (G-23b); UMUTZ-CnidG-35, Misaki, Sagami Bay, Japan sp. no. 19; UMUTZ-CnidG-260 (G-35b), same data as UMUTZ-CnidG-35; UMUTZ-CnidG-261 (G-35c), same data as UMUTZ-CnidG-35; UMUTZ-CnidG-262 (G-35d), same data as UMUTZ-CnidG-35; UMUTZ-CnidG-36, Misaki, Sagami Bay, Japan; UMUTZ-CnidG-263 (G-36b), same data as UMUTZ-CnidG-36; UMUTZ-CnidG-264 (G-36c), same data as UMUTZ-CnidG-36; UMUTZ-CnidG-265 (G-36d), same data as UMUTZ-CnidG-36; UMUTZ-CnidG-37, Misaki, Sagami Bay, Japan, coll. K. Kinoshita, summer 1906; UMUTZ-CnidG-266 (G-37b), same data as UMUTZ-CnidG-37; UMUTZ-CnidG-267 (G-37c), same data as UMUTZ-CnidG-37; UMUTZ-CnidG-269 (G-37e), same data as UMUTZ-CnidG-37; UMUTZ-CnidG-38, Cape Makurazaki, Kagoshima Prefecture, coll. M. Miyajima by diving, 7 August 1899; UMUTZ-CnidG-42, Misaki, Sagami Bay, Japan, 1–5 April 1917; UMUTZ-CnidG-272 (G-42b), same data as UMUTZ-CnidG-42; UMUTZ-CnidG-43, Misaki, Sagami Bay, Japasp. n. no. 77; UMUTZ-CnidG-273 (G-43b), same data as UMUTZ-CnidG-43; UMUTZ-CnidG-274 (G-43c), same data as UMUTZ-CnidG-43; UMUTZ-CnidG-275 (G-43d), same data as UMUTZ-CnidG-43; UMUTZ-CnidG-276 (G-43e), same data as UMUTZ-CnidG-43; UMUTZ-CnidG-44, Shimoda Harbour, Izu Peninsula, Japan, vessel Ohnoura-maru cruise, coll. S. Hirota, 28 August 1893; UMUTZ-CnidG-277 (G-44b), same data as UMUTZ-CnidG-44; UMUTZ-CnidG-278 (G-44c), same data as UMUTZ-CnidG-44; UMUTZ-CnidG-116, near Misaki Marine biological Station, Sagami Bay, Japan, coll. I. Ijima by diving, 1913; UMUTZ-CnidG-192, Moroiso, Misaki, Sagami Bay, Japan, collected by diving, 12 August 1904; UMUTZ-CnidG-196, Shimo-Chikura, Kagoshima Prefecture, Japan, coll. M. Miyajima by coral net, 12 July 1899; AKM 1633, Kominato, Japan, April 1944, deposited in Aikappu Museum of Natural History, Akkeshi Marine Station, Field Science Center for Northern Biosphere Hokkaido University; BIK-G224, Saba-shima Is. Koga Bay, Oga Peninsula, Sea of Japan, 7 m, coll. Y. Sato. 14 July 1988; BIK-G226, same data as BIK-G224; RMNH Coel. 41914 (AKM 594), Entrance of Otsuchi Bay, Otsuchi, Iwate Prefecture, 39°21.858'N, 141°59.972'E, 65.6 m, R/V Yayoi, coll. A.K. Matsumoto, 12 September 2005; RMNH Coel. 41915 (AKM 614), same data as RMNH Coel.41914; RMNH Coel. 41916 (AKM 615), Entrance of Otsuchi Bay, Iwate Prefecture, 39°21.917'N, 142°00.031'E, 77.6 m, R/V Yayoi, St.1(=St.2) 1 m biological dredge, coll. A.K. Matsumoto, 12 September 2005; RMNH Coel. 41917 (AKM 618), same data as RMNH Coel.41916; RMNH Coel. 41918 (AKM 619), off Ohako-zaki Cape, Otsuchi Bay, Iwate Prefecture, 39°21.428'N, 142°00.520'E, 69.2 m, R/V Yayoi, St.2(=St.5), 1 m biological dredge, coll. A.K. Matsumoto, 12 September 2005; RMNH Coel. 41919 (AKM 622), same data as RMNH Coel.41918; RMNH Coel. 41920 (AKM 1200), off Ohako-zaki Cape, Otsuchi Bay, Iwate Prefecture, ca. 39°21'N, 142°00'E, ca. 90 m, local fishery boat Taku-maru, gill-net, coll. K. Morita, ca. 21 March 2008; RMNH Coel. 41921 (AKM 1201), same data as RMNH Coel.41920; RMNH Coel. 41922 (AKM 1204), off Ohako-zaki Cape, Otsuchi Bay, Iwate Prefecture, ca. 39°21'N, 142°00'E, ca. 90 m, local fishery boat Taku-maru, gill-net, coll. K. Morita, 2 May. 2008; RMNH Coel. 41923 (AKM 1252), off Ohako-zaki Cape, Otsuchi Bay, Iwate Prefecture, ca. 39°21'N, 142°00'E, ca.75 m, local fishery boat Taku-maru, gill-net, coll. K. Morita, 9 May 2008; RMNH Coel. 41924 (AKM 1526), off Oshima Is. Entrance of Otsuchi Bay and Funakoshi Bay, Iwate Prefecture, 39°22.085'N, 142°01.152'E, 97 m, R/V Yayoi, 1 m biological dredge, coll. A.K. Matsumoto, 26 April 2010.

Colony bushy with few anastomoses. Branches flattened in the plane of branching and polyps arranged bilaterally. Points with slightly bent spindles up to 0.20 mm long, distal end with more developed tubercles (Fig. 38a). Collaret with bent spindles up to 0.25 mm long, middle part with more developed tubercles. Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 38b). These platelets are up to 0.10 mm long. Pharynx with straight spiny rods, up to 0.05 mm long. Coenenchyme with capstans (Fig. 38c), 0.07–0.08 mm long and small clubs of similar length (Fig. 38d). Furthermore spindles (Fig. 38e), unilaterally spinose spindles (Fig. 38f) and unilaterally spinose spheroids (Fig. 38g) are present, 0.10–0.30 mm long. All with simple and complex tubercles. The calyces with additional clubs, up to 0.20 mm long (Fig. 38h). The axis has smooth and sparsely tuberculate rods (Fig. 38i).

Red with yellow polyps. Variation: red (most colonies), pink, with yellow or white polyps, tentacle and pharynx sclerites colorless, all others orange; or colonies yellow with all sclerites yellow; or white with yellow polyps with polyp sclerites yellow and all others colorless. RMNH Coel. 41923 is rather unique in having a pale light brown colony, tentacle sclerites colorless, others colorless, partly white and partly yellow, or entirely yellow.

M. japonica is found at the eastern Pacific side of Japan; Sagami Bay, Izu Peninsula, Boso Peninsula, Nagasaki (Kyushu Is.), Shimo-Chikura (Kagoshima Prefecture, Kyushu Is.), Cape Makurazaki (Kagoshima Prefecture, Kyushu Is.), Otsuchi Bay (Sanriku, Iwate Prefecture); and at the western Sea of Japan side; Oga peninsula(Akita Prefecture) (Fig. 55).

The examined type material of Mopsella japonica was fragmented. In Harvard we only found one microscope slide (MCZ 4265, ALCY-412), in London only dried sclerites of the Harvard material (BMNH 1946.1.14.207). The type colony seems to be lost. Only in Vienna we found complete specimens identified as M. japonica; NHMW 8046, NHMW 8047 (Fig. 37b) and NHMW12690 identified as M. japonica, the sclerites resemble those of the type material (Figs 39, 40). The collector of NHMW 8046, Dr. Albrecht von Roretz visited Japan as a medical attaché of Austria (= Hungarian legation) between 1875–1879 and possibly collected this material. NHMW 2426 (M. flabellifera) and NHMW 8047 were collected by Dr. Richard. v. Drasche. He visited Japan during the Far East expedition 1875–1876. The Ostasiatisches Expedition by Baron Eug. V. Ransonnet, during which NHMW 12690 was collected, happened in 1873 (Matsumoto 2013, submitted).

Despite the small remainder of the type we could link it with other species described from Sagami Bay. Apparently this is the most common shallow-water species of the region, Kükenthal (1908) mentioned 40 specimens for his Melitodes flabellifera. We examined ZMB 5822 (Figs 36b, 41, 42) and NHMW 2426 (Figs 36e, 43, 44). They both are similar to M. japonica.

M. densa is also reported to occur in shallow water. According to Kükenthal (1909) it resembles M. flabellifera very much but differs in having more spinose collaret and point sclerites, more densely, stronger ornamented coenenchymal sclerites, and the color always being red with yellow polyps. Later, he separated the two species with M. densa having no clubs (Kükenthal 1924). The ZMB 5801 colony examined by us (Fig. 36c) showed many disintegrated sclerites (Figs 45, 46). As this mostly concerned the smaller sclerites we were unable to show the capstans and small clubs. But we found a few larger calyx clubs, apparently overlooked by Kükenthal (1909). Also most point sclerites were badly damaged. We also examined ZMB 5809 (Fig. 36d), which had its sclerites less disintegrated (Figs 47, 48).

Kükenthal (1924: 53) referred Pleurocorallium confusum to Pleurocoralloides. Bayer and Cairns (2003: 222) suggested that the species belongs to Acabaria. Moroff (1902a, b), in his descriptions of the species, mentioned flattened branches; polyps on one side of the colony; sclerites straight or bent 0.25 mm long spindles; also plate-like sclerites and crosses present; colony red with yellow polyps. The type seems to be lost. Because of its flattened branches we consider P. confusum synonymous with M. japonica.

Bayer and Cairns (2003: 222) suggested Pleurocoralloides formosum to belong to Acabaria. It was described as having polyps with 7 spindles per point and 6 rows in the collaret; sclerites orange, tentacles ones yellow, axis orange. We consider it a synonym of M. japonica; the colonies are shown in Fig. 36a, its sclerites are depicted in Figs 49, 50.

M. flabellifera has been described with two variations: M. flabellifera var. reticulata from Sagami Bay, 80–250 m depth. It differs in having many anastomoses, and no flattened branches, color orange red, sclerites bigger and more spinose. Depository of material is unknown.

M. flabellifera var. cylindrata from an unknown locality in Japan also lacks flattened branches, color red with yellow polyps, sclerites are less spinose. Two syntypes are reported to be in Frankfurt, SMF 1260 and 1262, but we could not find these specimens during a visit.

In northern Japan we found quite a number of specimens: RMNH Coel. 41915–41924. As an example we show the colony of RMNH Coel. 41922 (Fig. 37c) and its sclerites (Figs 51, 52). Here, the smallest colonies are white or yellow, only RMNH Coel. 41922 is red.

We found three specimens with extreme slender sclerites: BIK-G224 (Fig. 37a; sclerites Figs 53, 54), BIK-G226, and RMNH Coel. 41914.

Holotype RMNH Coel. 41925 (AKM 1148), off Kerama Isls., Okinawa Prefecture, Japan, 26°09.45'N, 127°26.90'E – 26°09.65'N, 127°26.81'E, 85–71 m, R/V Tansei-maru, KT08-33, St. KR-09, Chain Bag Dredge, coll. A.K. Matsumoto, 15 December 2008; paratype RMNH Coel. 41926 (AKM 1139), off Kerama Isls., Okinawa Prefecture, Japan, 26°12'N, 127°30'E, 56–51 m, R/V Tansei-maru, KT08-33, st. KR-10, coll. A.K. Matsumoto, 15 December 2008.

The holotype is a 12 cm long fragment without holdfast (Fig. 56a). At the base the stem is 1 cm wide, the end branches are only 1 mm wide. The polyps are situated laterally on the branches, the calyces hardly project beyond the coenenchyme and most polyps are retracted. Points with slightly bent spindles up to 0.20 mm long, distal end with more developed tubercles (Fig. 57a). Collaret with bent spindles up to 0.25 mm long, middle part with more developed tubercles (Fig. 57b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 57c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 57d). Coenenchyme with predominantly capstans (Fig. 57e), double disks (Fig. 57h), and small clubs (Fig. 57f), 0.05–0.08 mm long. Spindles (Fig. 58a) and disk spindles (Fig. 58b) are also common, 0.10–0.15 mm long. The calyces with additional leaf clubs, up to 0.15 mm long (Fig. 58c).

Colony red with white calyces and polyps. Coenenchymal sclerites orange, calyx and polyp sclerites colorless.

The paratype is very much alike the holotype regarding color and sclerites.

The species is only known from the Kerama Islands (Fig. 65).

Etymology. The species is named after its type locality, the Kerama islands.

The species mostly resembles M. abyssicola but differs in having longer disk spindles but shorter normal spindles. It also has more finely sculptured polyp sclerites.

Syntype ZMB 5807, Sagami Bay (Japan), 80-250 m (label 600 m), coll. Doflein 1904/05; previously unidentified museum material: ZMUC ANT-000595, Okinose, Sagami Sea, 60 fms (86–110 m), coll. Dr. Th. Mortensen, 11 June 1914; ZMUC ANT-000649, same data as ZMUC ANT-000595; UMUTZ-CnidG-19, Kashiwa-jima Is. Tosa, Kochi Prefecture, Japan, probably collected by K. Kinoshita during his Kashiwa-jima Is. Coral Ground Expedition, June 1909; UMUTZ-CnidG-27, coral ground, Uji Isls. Satsuma, Kanogshima Prefecture, Japan, ca. 80 fms (114–121 m), Kinoshita leg. coll. K. Kinoshita, June 1908; AKM 443, Sakai Port, Minabe, Wakayama Prefecture, ca.33°7445'N, 135°3329'E, shallower than 100 m, lobster-net, coll. A.K. Matsumoto, 1 April 2003; AKM 572, Otsuki, Tosa, Kochi Prefecture, 32°43'N, 132°48'E, 84.75-83.1 m, local fishermen’s boat, Kiryo-maru, coral net, st. 3, coll. A.K. Matsumoto, 7 October 2004; AKM 740, off Sata-misaki Cape, Kagoshima Prefecture, 31°00.50'N, 130°35.09'E – 31°01.3211'N, 130°34.6509'E, 178-189 m, R/V Tansei-maru, KT07-1, st. SM-2, coll. A.K. Matsumoto, 23 February 2007; AKM 904, Hachijo Is. Izu Isls., 33°20.9082'N, 139°41.1841'E – 33°21.0775'N, 139°40.4931'E, 213-185 m, R/V Tansei-maru, KT07-31, st. 14, coll. A.K. Matsumoto, 26 November 2007; AKM 1575, Takase west, Izu Is., Japan, ca. 34°21'N, 138°52'E – 34°26'N, 139°07'E, 221–244 m, R/V Tansei-maru, KT-87-19 cruise, St. TW02, large cylindrical dredge, coll. Suguru Ohta, 8 December1987; AKM 1594, SE off Taito-Saki, Boso, Chiba Prefecture, 35°05.086'N, 140°51.718'E – 35°04.176'N, 140°50.921'E, 975–1027 m, R/V Tansei-maru, KT03-17, St. TS6-3, 3 m ORE beam trawl, coll. Suguru Ohta, 17 November 2003; AKM 1601, Otsuki, Tosa, Kochi pref., 32°37.66'N, 132°50.44'E –32°37.56'N, 132°47.88'E, 114 m, local fishermen’s boat, Kiryo-maru, St.1, coll. A.K. Matsumoto, 7 October 2004.

Colony branched in one plane with few anastomoses (Fig. 56b). Points with slightly bent spindles up to 0.25 mm long, distal end with more developed tubercles (Fig. 59a). Collaret with bent, rather smooth spindles up to 0.30 mm long, middle part with tubercles (Fig. 59b). Tentacles with platelets, the larger ones crescent-shaped (Fig. 59c). These platelets are up to 0.18 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 59d). Coenenchyme with spindles 0.10–0.25 mm long (Fig. 60), with simple or complex tubercles. The axis has smooth and sparsely tuberculate rods (Fig. 59e).

Colony white, sclerites colorless.

ZMUC ANT-000649 showed somewhat longer spindles, up to 0.40 mm long (Figs 61, 62).

Pacific side of Japan (Fig. 65); northern limit is Sagami Bay.

The species is easily recognized by its white colony color, rather smooth polyp sclerites, and presence of spindles only.

Neotype SMBL-Cni1017, Sai, Mutsu Bay, Aomori Prefecture, close to Tsugaru Straits between Sea of Japan and NW Pacific, 5 m, coll. M. Nishihira and Hoshiai, 13 August 1964.

Colony broken up, consisting of three fragments, bushy with few anastomoses. The largest fragment is 7.3 cm long without holdfast (Fig. 56c). At the base the stem is 7 mm wide, the end branches are 2 mm wide. The polyps are arranged randomly, the calyces hardly project beyond the coenenchyme and most polyps are retracted. Points with slightly bent spindles up to 0.30 mm long, distal end with more tubercles (Fig. 63a). Collaret with bent spindles up to 0.30 mm long, middle part with tubercles (Fig. 63b). Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 63c). Coenenchyme with predominantly spindles, 0.10–0.25 mm long (Figs 63f, 64), with simple or complex tubercles. Capstans are also present, 0.05–0.10 mm long (Fig. 63e). The axis has smooth and sparsely tuberculate rods (Fig. 63d).

Colony red, sclerites orange.

Only known from the northern tip of the main island of Japan, Honshu Is. (Fig. 65).

The tentacle platelets were missing. The description and images provided by Minobe are inadequate to identify melithaeids and we were unable to find the depository of the material. As Minobe’s material was collected near Sai, as is our material, we concluded that we have the same species and designated a neotype here. The species is similar to M. corymbosa, but lacks clubs in the calyces and disk spindles in the coenenchyme.

Syntype, BMNH 1947.3.22.6, New Hebrides, Challenger st. 177, 60-120 fms (86-219 m), dried sclerites, coll. Prof. S.J. Hickson; syntype, BMNH 89.5.27.117, Hyalonema-Ground (Nishi-no yodomi), South of Japan, 35°11'N, 139°28'E, Challenger st. 232, 345 fms (631 m), 12 May 1875, figured specimen (= Acabaria nodosa Prof. Hickson), old label book 2, p. 12; syntype, BMNH 89.5.27.118 Hyalonema-ground (Nishi-no yodomi), south of Japan, 35°11'N, 139°28'E, Challenger st. 232, 345 fms (631 m), bottom green mud, 12 May 1875, figured specimen (= Acabaria nodosa Prof. Hickson), old label book 2, p. 12.

BMNH 89.5.27.117 (Fig. 66b): Points with slightly bent spindles up to 0.20 mm long, distal end with more developed tubercles (Fig. 67a). Collaret with bent spindles up to 0.25 mm long, middle part with more developed tubercles (Fig. 67b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 67c). These platelets are up to 0.10 mm long. Pharynx with straight spiny rods, up to 0.035 mm long (Fig. 67d). Coenenchyme with spindles (Fig. 67e) and unilaterally spinose spindles (Fig. 67f), 0.08-0.23 mm long, with simple tubercles. The calyces with additional clubs, up to 0.20 mm long (Fig. 67g).

Reddish brown, polyps yellow, axis yellowish-red; reddish nodes. Sclerites yellow, those of the polyps a bit paler, the smallest tentacle and the pharynx sclerites colorless.

BMNH 89.5.27.118 (Figs 66c; 68) and BMNH 1947.3.22.6 (Fig. 66a) have similar color patterns, BMNH 1947.3.22.6 has wider coenenchymal sclerites (Fig. 69).

New Hebrides, Sagami Bay (Fig. 74).

Wright and Studer (1889) mentioned that the colony may have been about 130 mm in height and 60 to 80 mm in diameter. Only BMNH 89.5.27.117 has this size (Fig. 66b), BMNH 89.5.27.118 is much smaller (Fig. 66c), BMNH 1947.3.22.6 consists of only a few fragments (Fig. 66a). Based on these colony sizes we conclude that these authors used BMNH 89.5.27.117 for their description.

Holotype RMNH Coel. 41927 (AKM 408), Watari-se bank, off Izu Isls., 34°02.8620'N, 138°54.8090'E – 34°02.9190'N, 138°54.6810'E, 101.1-106.2 m, R/V Tansei-maru, KT04-06 cruise, St.WS-2, 1m ORI Dredge, coll. A.K. Matsumoto, 30 April 2004; paratype RMNH Coel. 41928 (AKM 1606), Takase West, Izu Ridge, 34°26.5'N, 139°07.2'E, 104–127 m, R/V Tansei-maru, KT87-19, St. TW1, coll. S. Ohta, 8 December 1987.

The holotype is a 8 cm long fragment with holdfast (Fig. 66d). At the base the stem is 3 mm wide, the end branches are only 1 mm wide. The polyps are situated bilaterally on the branches, the calyces are dome-shaped, and most polyps are expanded. Points with slightly bent spindles up to 0.20 mm long, distal end with leaves (Fig. 70a). Collaret with bent spindles up to 0.30 mm long, middle part with more developed tubercles (Fig. 70b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 70c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 70d). Coenenchyme with predominantly capstans, double disks (Fig. 70f) and disk spindles (Figs 70g, 71c), 0.05–0.15 mm long, and small clubs (Fig. 71a), up to 0.10 mm long. Spindles are also present, 0.10-0.25 mm long, with simple tubercles (Fig. 71d). The calyces with additional clubs, up to 0.15 mm long (Fig. 71b).

Colony orange with yellow polyps, coenenchymal sclerites orange, polyp ones yellow.

RMNH Coel. 41928 has similar sclerites and color.

Off the Izu Islands (Fig. 74)

The species is named after Mr. T.J.G.M. van Oyen (NBC) in appreciation of the many microscope slides he prepared for the second author.

The species mostly resembles Melithaea abyssicola but has overall somewhat larger sclerites, a difference difficult to notice when not having both species at hand. However, the double disks of M. oyeni sp. n. are strikingly different, much wider than those of M. abyssicola (compare Fig. 70f with Fig. 3b).

Holotype UMUTZ-CnidG-32, Nakagusuku Bay, Okinawa Prefecture, Japan, diving, 16 April 1901; paratypes, UMUTZ-CnidG-254, same data as holotype; UMZC I.36300, S.W. Japan. T. Mizobuchi (purchased). Reg. Jan. 31.1903, 16.

The holotype is a 14.5 cm long fragment without holdfast (Fig. 66e). At the base the stem is 15 mm wide, the end branches are only 1 mm wide. The polyps are situated on one side of the colony, the calyces hardly project beyond the coenenchyme, and most polyps are retracted. Points with slightly bent spindles up to 0.10 mm long, distal end with more developed tubercles (Fig. 72a). Collaret with bent spindles up to 0.15 mm long, middle part with more developed tubercles (Fig. 72b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 72c). These platelets are up to 0.10 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 72d). Coenenchyme with predominantly capstans (Fig. 73a, d), double disks (Fig. 73b) and disk spindles (Fig. 73c), 0.05–0.10 mm long, and small clubs with rounded heads, 0.05 mm long (Fig. 72f). Spindles are also present, 0.10–0.20 mm long, with complex tubercles (Fig. 73e). The calyces with additional clubs, up to 0.14 mm long (Fig. 72g). The axis has smooth and sparsely tuberculate rods (Fig. 72e).

Colony orange with yellow polyps. Part of calyx sclerites and all polyp sclerites yellow, all others orange.

Okinawa, Japan (Fig. 74).

The material of UMUTZ-CnidG-32 was probably collected during the Ryukyu (= Okinawa) expedition by K. Mitsukuri and I. Ikeda, in April, 1901. UMZC I.36300 is dried material. According to us this is Melithaea sp. A of Aquilar-Hurtado et al. (2012) as the sclerite images given by them resemble ours. Melithaea ryukyuensis mostly resembles M. abyssicola, which has overall larger sclerites but much smaller spindles in the coenenchyme.

Holotype RMNH Coel. 41929 (AKM 840a), East of Jogashima Spur, 35°03.52'N, 139°37.43'E – 35°04.17'N, 139°37.52'E, 397–286 m, R/V Tansei-maru, KT07-31, st.8, coll. A.K. Matsumoto, 25 November 2007; paratypes: ZMUC ANT-000657, Sagami Bay, Okinose, 200 fms (286–366 m), Coll. Mortensen, 1 July 1914; ZMUC ANT-000660, same data as ZMUC ANT-000657; RMNH Coel. 41930 (AKM 243), South of Mera-se-minami Knoll, Sagami Bay, 34°54.8'N, 139°39.7'E – 34°54.8'N, 139°39.9'E, 312–348 m, R/V Shinyo-maru, St. 10, coll. A.K. Matsumoto, 18 October 2003; RMNH Coel. 41931 (AKM 244), same data as RMNH Coel. 41930; RMNH Coel. 41932 (AKM 247), South of Mera-se Minami Knoll, 34°54.8'N, 139°39.7'E – 34°54.8'N, 139°39.9E, 315-365 m, R/V Shinyo-maru, coll. A.K. Matsumoto, 18 October 2003; RMNH Coel. 41933 (AKM 593), Entrance of Otsuchi-bay, Iwate Prefecture, 39°21.858'N, 141°59.972'E, 65.6 m, R/V Yayoi, 1 m biological dredge, coll. A.K. Matsumoto, 12 September 2005; RMNH Coel. 41934 (AKM 835), Off Sendai, Miyagi Prefecture, depth over 100 m, trawl, coll. Hagihara, June 2007; RMNH Coel. 41935 (AKM 1605), West off Izu-Oshima, Sagami Sea, 410–440 m, R/V Hakuho-maru, KH-78-05, st. BS8, 2 m S.-A. beam trawl, coll. S. Ohta, 9 December 1978; BMNH 62.7.16.62(61?), off Okushiri Is., 3 miles off shore, Sea of Japan, 41°59'N, 138°30'E, 25-30 feet.

The holotype (RMNH Coel. 41929) consists of a number of branches probably belonging to one colony broken up while collecting (Fig. 75a). The largest fragment is 2.8 cm long. A holdfast or anastomoses are not present. The polyps are situated on one side of the colony. The calyces are dome-shaped, about 0.5 mm high and 1 mm wide; most polyps are retracted. Points with slightly bent spindles up to 0.25 mm long, distal end with more developed tubercles (Fig. 76a). Collaret with bent spindles up to 0.40 mm long, middle part with more developed tubercles (Fig. 76b). Tentacles with platelets, the larger ones crescent-shaped (Fig. 76c). These platelets are up to 0.15 mm long and have almost no tuberculation. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 76d). Coenenchyme with capstans 0.05-0.07 mm long, unilaterally spinose spindles (Fig. 77b), small clubs of the same length as the capstans, and spindles 0.10-0.20 mm long (Fig. 77a); all with simple tubercles. The calyces with additional leaf clubs, up to 0.15 mm long (Fig. 76e).

White, all sclerites colorless.

The paratypes are also fragmented. RMNH Coel. 41930, ZMUC ANT-000657 and ZMUC ANT-000651 are also white. ZMUC ANT-000660, RMNH Coel. 41931 and RMNH Coel. 41932 are yellow with yellow sclerites. BMNH 62.7.16.62(61?), RMNH Coel. 41934 and RMNH Coel. 41933 came from northern Japan, all three being red and from shallower depth. RMNH Coel. 41931 has somewhat more developed sclerites (Figs 78, 79).

Pacific side of Japan; Sagami Bay, off Sendai (Miyagi Prefecture), Otsuchi Bay (Sanriku, Iwate Prefecture); and Sea of Japan side, off Okushiri Is. (Fig. 86).

The species is named after the type locality, Sagami Bay.

We included BMNH 62.7.16.62(61?) in Melithaea sagamiensis sp. n. despite its slightly different sclerites (Figs 80, 81). We were not certain about the collection number, hence the “62(61)?”.

Holotype RMNH Coel. 41936 (AKM 743), Off Sata-misaki Cape, Kagoshima Prefecture, Japan, 30°56.0025'N, 130°44.2299'E – 30°56.2953'N, 130°43.3981'E, 116-120 m, R/V Tansei-maru, KT07-1 cruise, St. SM-1, Chain Bag Dredge, coll. A.K. Matsumoto, 23 February 2007.

The holotype is a 16.5 cm long colony with holdfast (Fig. 75c). At the base the stem is 10 mm wide, the end branches are only 1 mm wide. On the lower half of the colony the polyps are situated on one side of the colony; the upper part has polyps all around the branches. The calyces are dome-shaped, and most polyps are expanded. Points with slightly bent spindles up to 0.20 mm long, distal end with more developed tubercles (Fig. 82a). Collaret with bent spindles up to 0.30 mm long, middle part with more developed tubercles (Fig. 82b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 82c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 82d). Coenenchyme with predominantly capstans (Fig. 82f), double disks (Fig. 82g), and unilaterally foliate spheroids (Fig. 83b), 0.05–0.15 mm long, and small clubs (Fig. 82h), up to 0.10 mm long. Spindles are also present, 0.10-0.25 mm long, with simple or complex tubercles (Fig. 83c). The calyces with additional clubs, up to 0.15 mm long (Fig. 83a). The axis has smooth and sparsely tuberculate rods (Fig. 82e).

Colony orange with yellow polyps, coenenchymal sclerites orange, polyp ones yellow.

Off Cape Sata misaki, Kagoshima Prefecture (Fig. 86).

The species is named after the type locality, Satsuma, the old name of Kagoshima Prefecture.

This species is unique by its unilaterally foliate spheroids and spindles with complex tubercles.

Holotype ZMUC ANT-000565, off Nagasaki, 32°22'N, 128°42'E, 170 fms (311 m), 25 December 1900, coll. Suenson.

Colony branched in one plane, with slender branches (Fig. 75d). Points with slightly bent spindles up to 0.30 mm long, distal end with more developed tubercles or leaves (Fig. 84a). Collaret with bent spindles up to 0.35 mm long, middle part with more developed tubercles (Fig. 84b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 84c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 84d). Coenenchyme with capstans (Fig. 84e) and disk spindles (Figs 84f, 85c), 0.05–0.15 mm long, and small clubs of similar length (Fig. 84g). Spindles are also present, 0.15–0.30 mm long, with simple or complex tubercles (Fig. 85b). The calyces with additional clubs, up to 0.20 mm long (Fig. 85a).

White with orange calyces and polyps. Sclerites of calyces and polyps faint pink, all others colorless.

Off Nagasaki, East China Sea (Fig. 86).

The species is named after the collector, E. Suenson, who belonged to the Telegraph company Great Nordic Ltd. (Store Nordiske), established in 1869 at Denmark (Matsumoto 2014, 2015).

This species resembles M. sagamiensis sp. n., but differs by its thicker coenenchymal spindles.

Holotype RMNH Coel. 41937 (AKM 948), Toshima Is., Izu Isls., 34°33.1102'N, 139°17.4102'E – 34°33.6524'N, 143 m, R/V Tansei-maru, KT07-31 (Kuramochi leg.) St. 22 (L-3-100), coll. A.K. Matsumoto; paratype: RMNH Coel. 41938 (AKM 941) Toshima Is., Izu Isl, 34°34.4640'N, 139°18.3760'E – 34°33.5601'N, 139°17.8631'E, 152–198 m, R/V Tansei-maru, KT07-31 (Kuramochi leg.) St. 21 (L-3-200), coll. A.K. Matsumoto.

The holotype (RMNH Coel. 41937) consists of a large number of branches probably belonging to one colony broken up while collecting (Fig. 87a). The largest fragment, with the holdfast, is 6.5 cm long. The stem is 10 mm long and 3 mm wide; branching is in one plane. A few anastomoses are present. The polyps are situated on one side of the colony. The calyces are dome-shaped, about 0.5 mm high and 1 mm wide. Many polyps are expanded. Points with slightly bent spindles up to 0.20 mm long, distal end with more developed tubercles (Fig. 88a). Collaret with bent spindles up to 0.25 mm long, middle part with more developed tubercles (Fig. 88b). Tentacles with platelets, the larger ones crescent-shaped (Fig. 88c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 88d). Coenenchyme with capstans (Fig. 89a) 0.05–0.07 mm long, several slightly unilaterally foliate (Fig. 89b), unilaterally foliate spindles (Fig. 89c), small clubs of the same length as the capstans (Fig. 88e); spindles 0.10–0.25 mm long (Fig. 89d); all with simple tubercles. The calyces with additional clubs, up to 0.20 mm long (Fig. 88f).

Colony white with the larger yellowish nodes shining through the coenenchyme. All sclerites colorless.

Izu Isls (Fig. 98).

Etymology. The species is named after the R/V Tansei-maru.

The paratype (RMNH Coel. 41938) is just a fragment of colony, only three cm long with characters alike those of the holotype. The species mostly resembles M. tenuis but differs in having much wider coenenchymal spindles, up to 0.07 mm wide, twice as wide as in M. tenuis, in which they are only 0.03 mm wide. A few spindles in M. tenuis are wider, mainly caused by the spindles having bigger tubercles. Another difference is the slightly bigger capstans in the new species, but this is only noticeable when having both species.

Syntype ZMB 5799, Sagami Bay (Japan), 600 m (label 60-250 m), coll. Doflein,1904/05; previously unidentified museum material: BMNH 1921.10.26.9-2, Misaki, Sagami Bay, 200 fms (286–366 m), coll. A.V. Insole, May 1921; BMNH 1921.10.26.7, same data as BMNH1921.10.26.9-2; ZMUC ANT-000593, Sagami Bay, 400 fms, coll. Dr. Th. Mortensen, 2 July 1914; ZMUC ANT-000594, Sagami Bay, Japan, 80–120 fms (114–219 m), coll. Dr. Th. Mortensen, 6–19 June 1914; ZMUC ANT-000661, Sagami Sea, 300 fms (429–549 m), coll. Dr. Th. Mortensen, 29 June 1914; ZMUC ANT-000656, off Misaki Biological Station, Sagami Bay, 200 fms (286–366 m), coll. Dr. Th. Mortensen, 30 June 1914; ZMUC ANT-000651, Off Misaki, Sagami Bay, ca. 250 fms (ca.358–457 m), coll. Dr. Th. Mortensen, 10 June 1914; UMUTZ-CnidG-16, near Doketsuba, Sagami Bay, 170-180 hiro (243–272 m), coll. Kuma Aoki, 12 August 1895; UMUTZ-CnidG-198, Mera-no-hai-dashi-Oise line, Sagami Bay, 350 fms (500–529 m), coll. H. Matsumoto and H. Chiba, 21 July 1913; UMUTZ-CnidG-233, Gokeba, Sagami Bay, 150-20 hiro (227–29 m), coll. Kuma Aoki, 18 June 1902; AKM 142, East China Sea, R/V Tanisei-maru, KT02-03, st.E-5-1, 1 m Dredge, 19 April 2002; AKM 234, South of Mera-se Bank, Sagami-bay, 34°60.0'N, 139°40.2'E – 35°0.0'N, 139°40.3'E, 97–108 m, 17 October 2003; AKM 235, same data as AKM 234; AKM 413, Watari-se bank, Off Izu Isls., 34°02.8620'N, 138°54.8090'E – 34°02.9190'N, 138°54.6810'E, 101.1-106.2 m, R/V Tansei-maru, KT04-06, st. WS-2, 1 m ORI dredge, coll. A.K. Matsumoto, 30 April 2004; RMNH Coel. 41939 (AKM 414), same data; AKM 415, same data; AKM 421, same data; AKM 422, same data; RMNH Coel. 41940 (AKM 521), Otsuki, Tosa, Kochi prefecture, 132°50.44'E 32°37.66'N, – 132°47.88'E 32°37.56'N, 114 m, local fishermen’s boat Kiryo-maru, St. 1, coral net, coll. A.K. Matsumoto, 7 October 2004; AKM 663, off Tanabe, Wakayama Prefecture, 33°39.05'N, 135°09.89'E – 33°38.96'N, 135°10.16'E, 170.3-173.1 m, R/V Tansei-maru, KT05-30, st. TN-1 (1), coll. A.K. Matsumoto 26 November 2005; RMNH Coel. 41942 (AKM 664),same data as AKM663; AKM 670, off Tanabe, Wakayama Prefecture, 33°39.02'N, 135°09.89'E – 33°39.03'N, 135°09.07'E, 169.8-172.5 m, R/V Tansei-maru, KT05-30, TN-1 (2), coll. A.K. Matsumoto, 26 November 2005; AKM 745, off Satamisaki Cape, Kagoshima Prefecture, 30°56.0025'N, 130°44.2299'E – 30°56.2953'N, 130°43.3981'E, 116-120 m, R/V Tansei-maru, KT07-1, st.SM-1, Chain Bag Dredge, coll. A.K. Matsumoto, 23 February 2007; RMNH Coel. 41943 (AKM 980), Tsukura-se bank, Kagoshima Prefecture, East China Sea, 31°18.95'N, 129°46.15'E – 31°18.50'N, 129°45.96'E, 154–155 m, R/V Tansei-maru, KT08-3, St. NM05, ORI-TI Chain Bag Dredge, coll. A.K. Matsumoto, 6 March 2008; AKM 983, same data as RMNH Coel. 41943; AKM 1222, off Takarajima Is., Tokara Isls, East-China Sea, 29°05.29'N, 129°10.43'E, 334 m, R/V Tansei-maru, KT07-21, st. DT0203-1, Chain Bag Dredge, coll. Yokose, 31 August 2007; AKM 1230, same data as AKM1222; AKM 1598, Otsuki, Tosa, Kochi Prefecture, 32°37'N, 132°50'E, 114 m, local fishermen’s boat Kiryo-maru, st. 1, coll. A.K. Matsumoto, 7 October 2004; AKM 1600, Otsuki, Tosa, Kochi Prefecture, 32°43.08'N, 132°48.06'E – 32°43.12'N, 132°47.68'E, 84.75-83.1 m, local fishermen’s boat Kiryo-maru, st. 3, coll. A.K. Matsumoto, 7 October 2004.

Colony branched in one plane, with slender branches (Fig. 87b). Points with slightly bent spindles up to 0.15 mm long, distal end with more developed tubercles (Fig. 90a). Collaret with bent spindles up to 0.20 mm long, middle part with more developed tubercles (Fig. 90b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 90c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 90d). Coenenchyme with capstans (Fig. 91c), about 0.05 mm long, small clubs of the same length (Fig. 91a); unilaterally spinose spheroids and unilaterally spinose spindles up to 0.10 mm long (Fig. 91d); spindles are also present, 0.10–0.18 mm long (Fig. 91e). The calyces with additional clubs, up to 0.15 mm long (Figs 90e, 91b).

Colony red with white/yellow polyps, polyp sclerites colorless or yellow, all others orange.

Colonies can be yellow with all sclerites yellow or white with all sclerites colorless.

Sagami Bay, and now South to East China Sea (Fig. 98).

We did not examine ZMB 5805, syntype, Okinose Bank (Japan), 80–250 m, coll. Doflein 1904/05 because the material consists of only small fragments.

Holotype RMNH Coel. 41941 (AKM 1212), 28°54.90'N, 129°04.09'E, off Yokoate-jima, Tokara Islands, East China Sea, 395 m, R/V Tansei-maru, KT07-21, St. DY0205, Chain Bag Dredge, coll. Dr. H. Yokose, 30 August 2007.

Colony branched in one plane, broken up while collecting (Fig. 87c). The largest fragment being 12 cm long. The larger nodes are swollen and clearly visible. The polyps are situated on one side of the colony. The calyces are dome-shaped, about 0.5 mm high and 1 mm wide. Points with slightly bent spindles up to 0.25 mm long, distal end more tuberculate (Fig. 92a). Collaret with bent spindles up to 0.35 mm long, middle part with more developed tubercles (Fig. 92b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 92c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 92d). Coenenchyme with predominantly capstans, double disks (Fig. 93b) and disk spindles (Fig. 93c), 0.05–0.15 mm long, and small clubs (Fig. 92f), up to 0.10 mm long. Spindles are also present, 0.10–0.30 mm long, mostly with simple tubercles (Fig. 93d). The calyces with additional clubs, up to 0.25 mm long (Fig. 93a). The axis has smooth and sparsely tuberculate rods (Fig. 92e).

Colony red, all sclerites orange.

Only known from off the Tokara Islands. (Fig. 98).

Etymology. The species is named after the type locality, the Tokara Islands.

The species resembles M. abyssicola sp. n., M. oyeni sp. n., and M. satsumaensis sp. n., but differs in having rather smooth polyp sclerites and long calyx clubs.

Holotype ZMB 5803, Sagami Bay, Japan, 700 m, coll. Doflein, 1904/05; previously unidentified museum material: ZMUC ANT-000592, Sagami Sea, Japan, 500 fms (715-914 m), coll. Dr. Th. Mortensen, 25 June 1914; BMNH 1921.10.26.9-1, BMNH 1921.10.26.9-2, Misaki, Sagami Bay, 200 fms (286-366 m), coll. A.V. Insole, May 1921; MZS-Cni57, Sagami Bay, 200 m, coll. Doederlein. UMUTZ-CnidG-14, Niijima Is., Izu Isls., coll. sp. no. 80, 22 April; UMUTZ-CnidG-20, Dokesuba, Sagami Bay, 130 hiro (186–196 m), coll. Kuma Aoki, 9 August 1897; UMUTZ-CnidG-234, Mochiyama, Sagami Bay, 400 hiro (572–604 m), possibly coll. Kuma Aoki; AKM 502, Ose-zaki, Suruga Bay, 137–155 m, coll. K. Kitazawa, 22 July, 2004; RMNH Coel. 42030 (AKM 724), off Tanega-shima Is., East China Sea, 30°24.62'N, 131°08.46'E – 30°24.95'N, 131°08.32'E, 468-502 m, R/V Tansei-maru, KT07-1, st. TN-3, 1 m biological dredge, coll. A.K. Matsumoto, 23 February 2007; AKM 1034, Koshiki Knoll, off Kagoshima, East China Sea, 31°36'N, 129°19'E, 497-535 m, R/V Tansei-maru, KT08-3, st. KS-01, coll. A.K. Matsumoto, 6 March, 2008; AKM 1591, Danzyo-Basin, East China Sea, 31°58.02'N, 129°02.28'E – 31°59.30'N, 129°01.19'E, 711-801 m, R/V Tansei-maru, KT00-17, St. DZ-1, ORE Beam Trawl of 3 m span, coll. Suguru Ohta, 12 December 2000; AKM 1592, same data as AKM1591; AKM 1593, South East off Taito-saki Cape, Boso Peninsula, 35°05.086'N, 140°51.718'E – 35°04.176'N, 140°50.92'E, 975-1027 m, R/V Tansei-maru, KT03-17, st. TS6-3, coll. S. Ohta, 17 November 2003; AKM 1599, South off Daio-zaki Cape, Kumano-nada, 34°05'N, 136°51'E, R/V Tanisei-maru, KT94-07, st. KN25, 25 May 1994, 475-494 m, coll. S. Ohta; AKM 1604, west off Izu-Oshima, Sagami Bay, 139°15.0'E 34°40.4'N, 415-440 m, R/V Hakuho-maru, KH-78-05, st. BS8, 2 m S.-A. beam trawl (on label), 7 December 1978.

Colony branched in two parallel planes. Points with slightly bent spindles up to 0.25 mm long, distal end with more developed tubercles (Fig. 94a). Collaret with bent spindles up to 0.30 mm long, middle part with more developed tubercles (Fig. 94b). Tentacles with platelets, the larger ones crescent-shaped (Fig. 94c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 94d). Coenenchyme with capstans (Fig. 95b) about 0.05 mm long, several slightly unilaterally spinose, small clubs of the same length (Fig. 95a); spindles 0.10–0.30 mm long (Fig. 95c); all with simple tubercles. The calyces with additional clubs, up to 0.12 mm long (hardly present in type material). The axis has smooth and sparsely tuberculate rods (Fig. 94e).

Colony red, tentacle sclerites colorless, all others pink.

AKM 502 is yellow with yellow sclerites.

Southern Pacific coast of Japan, north to Sagami Bay, south to East China Sea; Suruga Bay, off Taito-Saki Cape, Boso Peninsula; off Tanega-shima Is., Koshiki Knoll., Danzyo Basin, off Kagoshima (Fig. 98).

The type specimen clearly has damaged sclerites, probably caused by formalin. Recently collected material shows less rounded sclerites (Figs 87e, 96, 97). Double disks are present but so poorly developed that they can hardly be recognized as such.

The species resembles M. tenuis but differs in having longer spindles (up to 0.30 mm long versus up to 0.18 mm long in M. tenuis), and lacking unilaterally spinose spheroids. It also resembles M. corymbosa, but that species has mostly more slender, shorter spindles. Moreover, M. undulata has poorly developed tentacle sclerites compared with the other two species.

Apparently the type material is mostly lost, only a small fragment remained (Fig. 87d) of a colony described as being 21 cm long (Kükenthal 1909).