Disk circular (dd = 0.63 to 4.79 mm). Covered by small, hyaline bifid or trifid spines, also on the radial shields (Fig. 2f). Radial shields longer than wide, separated by a row of scales (Fig. 2f). Ventral interradius covered by spines similar to dorsal (Fig. 2g). Bursal slits short and wide. Oral shields enlarged laterally, triangular, with distal margin (Fig. 2h). Adoral shields united proximally. No oral papillae, but jaws bear terminal clump of dental papillae (Fig. 2h). Dorsal arm plate fan-shaped (Fig. 2i). Ventral arm plate slightly longer than wide, hexagonal, with distal margin long and slightly concave (Fig. 2j). Nine long arm spines, vitreous and denticulate, the one but last smallest and the last modified into a hook. Single tentacle scale small.

Bermuda, North Carolina to Texas coast and offshore reefs, Dry Tortugas, the Bahamas, the Antilles, Mexican Caribbean, Honduras, Belize, Panama, islands off Caribbean, Colombia, Venezuela, Brazil, Uruguay, and off La Plata river, Argentina (Tommasi 1970, Devaney 1974, Hendler et al. 1995, Chavarro et al. 2004, Durán-Gonzáles et al. 2005, Laguarda-Figueras et al. 2005, Alvarado et al. 2008, Borrero-Pérez et al. 2008, Hernandéz-Herrejón et al. 2008, Martínez 2008). In Brazil from Amapá (Albuquerque 1986), Piauí (Gondim and Giacometti 2010), Paraíba (Rathbun 1879), Pernambuco (Tommasi 1970), Alagoas (Miranda et al. 2012), Bahia (Alves and Cerqueira 2000), Abrolhos off southern Bahia, Trindade oceanic island off Espírito Santo (Tommasi 1970), Rio de Janeiro (Rathbun 1879), São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul (Tommasi 1970). Intertidal to 540 m depth. Sampled between 10 and 34 m depth in this study.

Associated with seaweeds, such as the brown alga Sargassum spp. (Jacobucci et al. 2006), living between stones, and in sponges (Tommasi 1967), in oyster banks, mangroves, seagrass beds and on sessile animals such as Millepora sp. and gorgonians (Hendler et al. 1995). Also reported in Brazil from colonies of the octocoral Carijoa riisei (Neves et al. 2007), from the tubes of the polychaete Phyllochaetopterus socialis Claparède, 1870 (Nalesso et al. 1995), in the sponge Zygomycale parishii (Bowerbank, 1875) (Duarte and Nalesso 1996), and from colonies of the bryozoan Schizoporella errata (Walters, 1878) (Morgado and Tanaka 2001). Individuals with a disk diameter smaller than 4.0 mm do not have long spines on the median region of the dorsal disk surface (Monteiro 1987). This is a common and highly variable species, with planktotrophic larvae (Hendler 2005). It displays great variation in color, Tommasi (1970) listed 21 different color forms of this species (Hendler et al. 1995). On the coast of Paraíba, the most commonly observed color is violet or specimens which are violet only on the disk and have aniline-blue arms.