Sotoplax robertsi Guinot, 1984

(Figs. 1 A, C; 2A–C; 3A–C; 4; 5A–C; 6A–F; 7A, B; 8A, B)

Euryplax sp. Soto 1980: 93.

Sotoplax robertsi Guinot, 1984: 92, figs. 1–3, pl. 1, figs. A–D; Abele & Kim 1986: 55, 592, 600, 601, figs. a, b; Boschi 2000: 74; McLaughlin et al. 2005: 257; Ng et al. 2008: 78, 79; Almeida et al. 2008: 278; Coelho et al. 2008: 13; Thoma et al. 2009: 553, 558 [fig. 1], 563.

Material examined. Gulf of Mexico: 28°30’N, 84°58’W, cruise T7109 station no. 4, 54 m, R.V. Tursiops, L. Soto coll., 03.04.1971: holotype male (6.7 × 10.8 mm) (MNHN-B8740). – 28°34.24’N, 84°28.77’W, R.V. Pelican, NSF-III-049, D. L. Felder et al. coll., 04.07.2006: 1 male (4.4 × 7.1 mm), 1 male (damaged carapace, cl 4.7 mm), 3 pre-adults (2.7 × 3.6 mm; damaged carapace, cw 4.7 mm; damaged carapace) (ULLZ 7717). – South of Port Isabel, Texas, 26°20’N, 96°28’W, STOCS /BLM survey 4/IV- 2, R/V Longhorn, N. Rabelais et al. coll.: 1 ovigerous female (6.0 × 10.6 mm) (ULLZ 6437).

Brazil: Bahia, Camamu Bay, 13°54’14”S, 39°00’34”W, station 5, M. C. Guerrazzi coll., 24.06.2004: 1 male (3.1 × 4.9 mm), 1 pre-adult female (3.3 × 5.1 mm) (MZUESC 1196).

Diagnosis. See for family.

Geographical distribution. Western Atlantic: northeastern Gulf of Mexico and off central Brazil. Depth: 33– 54 m.

Remarks. The description and figures in Guinot (1984) are detailed and do not need to be elaborated upon here. They are supplemented by the detailed notes of Almeida et al. (2008).

The extent of the clump of plumose setae along the anterior margin of the cheliped carpus and the anterior portion of the inner margin of the merus is somewhat variable. The holotype male (MNHN-B8740) and Brazilian specimens (MZUESC 1196) lack these setae (Figs. 1 A, 7A), but is clearly evident on the recent males from the Gulf of Mexico (ULLZ 7717). In the adult female (ULLZ 6437), the setae are present but are relatively sparse (Fig. 8 A).

The press-button of the pre-adult female abdominal-locking mechanism is prominent, acute, and sharp (Fig. 7 B) but undiscernible in the adult females (Fig. 8 B).