Trapezia formosa Smith, 1869

(Fig. 8A)

Trapezia formosa Smith, 1869: 286 .— Castro 1997a: 81; 2009: 272.— Castro et al. 2004: 51.— Liu et al. 2008: 792 (list) (Taiwan Island, Xisha Islands).— Higashiji 2013: 88, fig. 2H (Ryukyu Islands).— Poupin 2018: 40, fig. 12K (Mayotte Island).

Trapezia digitalis var. formosa Borradaile 1902: 265

Material examined. Nansha Islands: Mischief Reef, Ziming Yuan, 115°32.5’E 9°55.7’N, 11 m, coll. Shaobo Ma, Yuli Sun, 5 May 2022, 1 male (5.44 × 4.20 mm), NS-MJJ-2022-1070; 115°34.4’E 9°53.5’N, 10 m, coll. Shaobo Ma, Yuli Sun, 10 May 2022, 1 female (5.05 × 4.29 mm), NS-MJ-2022-1736; 1 pre-adult (3.33 × 2.86 mm), NS-MJ-2022-1782; 1 pre-adult (3.46 × 2.88 mm), NS-MJ-2022-1799. Fiery Cross Reef, 113°0.8’E 9°39.9’N, 10 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 14 May 2022, 1 male (5.30 × 4.31 mm), 1 female (6.14 × 4.81 mm), NS-YS-2022-1162; 4 pre-adults (3.44 × 2.98 mm; 2.88 × 2.54 mm; 3.02 × 2.54 mm; 3.15 × 2.59 mm), NS-YS-2022-1229. — Zhongsha Islands: Shenhu Shoal, 113°0.7’ E 19°30. 3’ N, 17 m, coll. Geng Qin, Wei Jiang, 5 July 2020, 1 male (8.81 × 7.56 mm), 1 female (9.59 × 7.98 mm), ZS244C05. Helen Shoal, 113°51’E 19°11’N, 18 m, coll. Geng Qin, Wei Jiang, 5 June 2021, 1 female (9.79 × 7.16 mm), C11. — Xisha Islands: The Yongle Islands, 111°44.3’E 16°33.0’N, 10 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 22 May 2022, 1 male (6.77 × 5.54 mm), 1 female (4.26 × 3.49 mm), 1 pre-adult (3.82 × 3.27 mm), XS-YL-2002-1010; 1 male (7.01 × 6.12 mm), XS-YL-2002-1011. North island, 16°58’N 112°19’E, 10 m, coll. Shaobo Ma, November 2020, 1 male (6.89 × 5.66 mm), XSBS01. Found in Pocillopora ( Pocilloporidae) unless otherwise noted .

Geographical distribution. Across Indo–West Pacific and Eastern Pacific regions (Castro et al. 2004).

Remarks. The carapace is smooth oval, the width is about 1.3 times longer than the length. The simple node of carapace lateral is sometimes absent or so tiny that they can only be observed by a microscope. The carapace width of Trapezia formosa is between 4–6 mm, usually smaller than other species of Trapezia .