Plate 12

Lethrinus Moensii (part) Bleeker, 1855: 435, East Indies.
Lethrinella variegatus (not of Valenciennes); Smith, 1959: 291, p1. 22, figs. C, D, East Africa; Kyushin et al., 1977: 144, Andaman, Nicobar, Chagos.
Lethrinus variegatus (not of Valenciennes); Akazaki, 1962: 263, fig. 47, Amami Is., Wakayama (both in Japan); Shinohara, 1963: 42, fig. 2, Ryukyus; Sato, 1971: 139, fig. 13, Japan, Louisiades; Gushiken, 1972: 38, fig. 182, Okinawa I.; Kyushin et al., 1973: 66, Andaman Sea; Masuda et al., 1975: 60, fig. D, 234, southern Japan.
Lethrinus microdon (not of Valenciennes); Akazaki, 1962: 261, Kagoshima (Japan).
Lethrinus reticulatus (not of Valenciennes); Akazaki, 1962: 266, fig. 48, Kagoshima, Amami Is. (both in Japan); Munro, 1967: 327, p1. 43, New Guinea.

Specimens examined.

Holotype. —UMUTZ53991 (254mm standard length), purchased at Naha Fish Market, Okinawa I., Ryukyus on April 1, 1977.
Paratypes. —UMUTZ52619 (250), 52626 (276), 52623 (280), 52614 (282), 52627 (285), 52625 (287), 52618 (295), 52624 (295) from Bonin Is.
—MUTZ52601 (332) from Hachijo, Japan.
—FAKU33047 (199) from Wakayama, Japan.
—FAKU33034 (307) from Kagoshima, Japan.
—MIKU1955 (233) from Amami, Japan.
—UMUTZ52525 (259), 52436 (276) from Ishigaki I., Ryukyus.
—BPBM8557 (262) from Palau Is.
—UMUTZ52692 (165), 52693 (166), 52691 (202), 52690 (207), 52687 (208), 52685 (240), 52686 (245), 52689 (250), 52688 (265) from Louisiades.
—UMUTZ53996 (194) from Tutuila I., Samoas.
—RMNH5754 (1 of 2 individuals: 238) from East Indies.
—UMUTZ52897 (78), 52906 (165), HUMZ-A2434 (225), -A2428 (280) from Little Andaman I.

Diagnosis. —This new species is distinguished from other Lethrinus species by the combination of the following features: Head length more than body depth. End of jaws on the vertical through anterior nostril. Interorbital area flat or a little convex. 5 scale rows between lateral line and median dorsal spines. Inner base of pectoral without scales. A scaleless area, bright red when fresh, on the posterior end of operculum (Fig. 9-A). Lateral teeth of jaws conical (Fig. 3-D). Distribution of melano phores on pelvic fin membranes restricted (Fig. 4-C).

D. X, 9; A. III, 8; P₁. 13; P₂. I, 5; C. 8 + 7; L. lat. 46 to 48 (48 and 47 on left and right side of holotype respectively); Ltr. 5 or 6/i/14 or 15 (6/i/15 in holotype).

Proportional measurements of some specimens including the holotype are shown in Table 25.

The following description is of the holotype (327 mm total length). For the features common to all the species, see the description of the genus. Body slender and compressed, head length more than body depth which in turn double length of body width. Caudal peduncle narrow, 4.2 in standard length. Dorsal profile of head bending outward with an angle before eye and slightly concave above mouth, Interorbital area slightly convex. Jaws terminal, turning slightly upwards when they shut. End of jaws on the vertical through anterior nostril. Posterior nostril about halfway between anterior one and anterior border of eye. Lateral line gently curving along dorsal profile from upper end of opercular slit to center of caudal base.

First dorsal spine rather long and thin, its length about equal to orbit length. Second one thicker and 1.5 times as long. Third the longest, 1.2 times as long as second and about equal to suborbital length. Rest of spines gradually decreasing in length to last (tenth) which 4/5 length of first. Soft dorsal rays gradually decreasing in length from first which 1.2 times as long as last spine to last (ninth) which 4/5 length of first. Base of spinous portion 1.5 times as long as that of soft portion which about equal to snout length. Anal spines stout. First short, about 3/5 of second. Second about 9/10 of third which longest and equal to tenth dorsal spine. All of soft anal rays about equal length, equal to first dorsal ray and 4/5 of soft anal base. Caudal fin lunate, upper lobe longer than lower. Longest caudal ray stretching out beyond the shortest for about caudal peduncle depth. Pectoral fin reaching above anus. First (uppermost) ray about equal to orbit length and 1/3 of second. Second longest. Rest of rays then gradually decreasing in length to last (13th) which slightly longer than first. All pectoral rays except first, second, and 13th branched. Pelvic fin reaching anus. Pelvic spine equal to upper jaw length and about 7/10 of first ray. Rest of pelvic rays then gradually decreasing in length to last (fifth) which 1/2 of first. Axillary scale outside pelvic long and pointed posteriorly, equal to orbit length.

Scales on body ctenoid and of moderate size, smaller on head, thoracic region, and on basal areas of soft dorsal, soft anal, caudal, and pectoral. Predorsal scales not extending anteriorly beyond the vertical through preopercular end. Scales absent on axilla and inner base of pectoral. Area without scales on posterior end of operculum and on outside pectoral base.

Anterior teeth of jaws fine and conical, making a villiform bands, with two pairs of outside canines. Outer canines larger and moderately curving. 8-9 conical teeth on sides in a single row, central ones larger. (Fig. 3-D.)

Gill-rakers on the first arch of left side 5 (lower) + 5 (upper).

Color. —Grayish-green to purple, paler below. Head usually darker. Iris golden. Lips pink to red. Bright red spot on posterior end of operculum. Fins red to orange with brighter margin. Vertical fins usually mottled with brighter red. Pelvic paler.

Distribution. —East Africa to southern Japan, Samoas.

Remarks. —For the types of L. Moensii, see the remarks for L. semicinctus.

Etymology. —The name rubrioperculatus (with a red operculum) is a Latin adjective referring to the characteristic red spot on the posterior end of operculum.