Disc pentagonal, covered with soft skin, lacking disc scales. Oral shields covered by soft skin, large and wide, proximally pointed and distally rounded. Seven oral papillae, outermost small, next pair wider and innermost one more pointed; teeth are narrower. Arms 5 times disc diameter. Dorsal arm plates of great size, on younger specimens oval, in adults broader, more arched with rounded margins. Arm spines 7 in number, about half as long as the joint, completely naked, pointed, thin, strongly serrated and hyaline, resembling Ophiothrix .

Disc small (diameter 15 mm in specimen from Blake Reef, 19 mm in specimen from Alacranes Reef), pentagonal, covered with smooth skin. Radial shields covered by skin. Each jaw with 6-7 oral papillae, outermost rectangular with rounded tips, next 3 pairs pointed, infradental thicker and pointed. Oral shields elliptical, much broader than long, touching first lateral arm plate, with rounded tips. Adoral shields narrow. Genital slits prominent, thicker, not reaching periphery of disc. Five arms, longest one 95 mm long. Dorsal arm plates large, oval, twice as wide as long; some arm segments fragmented. Ventral arm plates quadrangular, covered by skin. Lateral arm plates enlarged and flared at distal ends; second lateral arm plate particularly enlarged, nearly reaching edge of disc. Six to 7 arm spines proximally in Blake Reef specimen and 7-8 arm spines in Alacranes Reef specimen, ventralmost the largest (2.5 mm), reaching almost 1 and one-half arm segments, distally 5-6 arm spines, terminal part of arms with 4-5 arm spines; pointed, hyaline, serrated, directed downwards. Tentacle pores large, widely open; each one armed with 2 large, elongated tentacle scales, outermost pore thicker and shorter than innermost one.

Color variation . The dorsal side of the Blake Reef specimen has a brown disc with yellow spots, the arms are also dark brown, and some arm segments and arm spines possess yellowish bands. The ventral surface of the disc is dark brown with yellow spots larger than those of the dorsal side. The disc of the Alacranes Reef specimen has a uniform purplish color, the arms are light purple; distally, some arm segments possess a yellowish band; spines are banded with yellow stripes; ventrally the mouth area is beige with brown interradial areas spotted with beige motes (Fig. 1).

Off The Bahamas, Belize, Puerto Rico, Saint Thomas and Panama (these localities lack precise geographical coordinates; Hendler et al., 1995; Hotchkiss, 1982), Veracruz and Yucatán, Mexico (Fig. 2). The latter 2 records expand its geographic distribution to the southwest Gulf of Mexico.

Figure 2

Bathymetric distribution . 1-24 m (Hendler et al., 1995; Hernández-Díaz, 2011).

ICML-UNAM 3.197.0, 1 specimen; Blake Reef, Gulf of Mexico (20°45′37.5″ N, 96°59′31.1″ W); 14 April 2013; 24 m depth. ICML-UNAM 10162, 1 specimen; Alacranes Reef, Gulf of Mexico, Yucatán, Mexico (22°27′09.8″ N, 89°45′44.9″ W), coral rubble on shallow reef flat; 13 August 2009, 2 m depth.

The genus Ophioblenna is poorly known and not well documented. Lütken (1859) described the genus for the West Indies, with O. antillensis as the only species. However, it has also been mentioned as Ophialcaea glabra H. L. Clark, 1901 and Ophiomitrella glabra H. L. Clark, 1901, but further information is needed regarding the systematic position of this species and the latter ones. Clark (1901) mentioned that the oral papillae of Ophialcaea glabra were very similar to those of Ophiacantha , but the taxon differed sharply from that genus in the arrangement of the dorsal arm plates, the arm spines, and the covering of the disc. In fact, the soft skin covering the disc, the pointed oral papillae and the number of arm spines characterized the genus Ophioblenna .

It has been reported that the ostracod Pontocypria hendleri is a commensal of this species (Hendler et al., 1995; Maddocks, 1987).

Ophioblenna antillensis was already reported for Mexico (Solís-Marín et al., 2013). However, recent analysis of the material deposited at ICML-UNAM shows that these records correspond to Ophiomyxa flaccida , hence these are the first records of O. antillensis for the Gulf of Mexico; they extend the geographic distribution of the species and highlight the need for further studies on the taxonomy and diversity of the echinoderm fauna of the Gulf of Mexico.

We thank Alicia Durán González (ICML, UNAM) for technical support. We also thank Conabio (Grant FB1194) for supporting the project "Esponjas, corales escleractinios, equinodermos y peces de los arrecifes coralinos del norte y sur de Veracruz"; SEP for partial support through "Bases para el Análisis y Síntesis de los Sistemas Costeros de Veracruz", conducted within the framework of the network for "Análisis y síntesis de la zona costera veracruzana, golfo de México" (RASZCOV). Permits (Dgopa. 02698.260312.0743 and Dgopa. 5458.170512.1381) were issued by Sagarpa. Conacyt-Semarnat, for financial support for expedition to Alacranes Reef (Project No. 10828).