Trianguloscalpellum regium (Thomson, 1878)

Figures 1 G, 10

Scalpellum regium Wyville Thomson, 1878: 11, figs 2–3. — Hoek, 1883: 106: pl. 4 figs 3–5. — Pilsbry, 1907: 28, pl. 3 figs 4, 5. — Gruvel, 1920: 30, pl. 1 fig. 7.

Trianguloscalpellum regium regium . — Zevina, 1981: 309, fig. 234.

Material examined. CEL-BB-46C, 1 specimen, Stn. CP375 (24º16.240’N, 122º11.720’E, 27 Aug. 2006, depth: 2216–2497 m), CL 36.3 mm, CW 22.50 mm, PL 16.78 mm.

Diagnosis. Capitulum quadrangular, covered by smooth membrane, 14 fully calcified plates; tergum large, triangular, carinal margin convex, occludent margin straight, umbo apical; scutum quadrangular, higher than wide, apex produced at junction of occludent and tergal margins, umbo apical; carinolatus higher than wide, curved, apex produced, umbo apical.

Description. Capitulum quadrangular, 14 plates, covered by smooth membrane (Fig. 1 G); tergum large, triangular, carinal margin convex, occludent margin straight, umbo apical; scutum quadrangular, higher than wide, apex produced at junction of occludent and tergal margins, umbo apical (Fig. 1 G); upper latus triangular, tergal and lateral margins convex, scutal margin concave (Fig. 1 G); inframedian latus equilateral triangle, umbo apical; rostrolatus very narrow, wider than high; carinolatus higher than wide, curved, apex produced, umbo apical (Fig. 1 G); carina bowed, roof flat; peduncle with densely packed, concentric scales (Fig. 1 G). Maxilla densely setose (Fig. 10 A); cutting edge of maxillule not notched,>22 large cuspidate setae along cutting edge (Fig. 10 B); mandible with 3 evenly separated teeth excluding inferior angle, lower margin long, naked, inferior angle covered by dense setae (Fig. 10 C); mandibular palp narrow, elongated, setae along superior margin, inferior margin naked (Fig. 10 D); labrum concave, cutting edge smooth, teeth absent (Fig. 10 E). Cirrus I separated from remaining cirri, rami unequal, outer ramus longer, slender, 10-segmented, inner ramus broader, shorter, 6-segmented (Fig. 10 F); cirrus II with rami equal, both rami 22-segmented (Fig. 10 G); cirrus VI with rami equal, outer and inner rami 33-segmented; caudal appendage short, 4-segmented, length <height of basal segment of pedicle of cirrus VI (Fig. 10 H).

Distribution. Cosmopolitan: Atlantic and Pacific Oceans, including Taiwan.

Remarks. This is a new record for Taiwanese waters. This species was named by the chief scientist, Professor Sir Charles Wyville Thomson (see Hoek, 1883: 106), but no detailed species description was provided. Hoek (1883) fully described the species and retained Thomson’s name, Scalpellum regium .