(Fig. 2F)
Pisosoma riisei Stimpson, 1859: 75.
Material examined. Brazil, São Paulo: 1 ♂, 1 ♀, CCDB 4902, Ubatuba, Ilha das Couves, colls. F. Mantelatto et al., 19.x.2012; 1 ♂, CCDB 3284, Ubatuba, Enseada de Ubatuba, Praia do Itaguá, coll. I. Leone, 03.iv.2011; 1 ♂, CCDB 2016, Ilhabela, Praia do Engenho d’Água, colls. F. Mantelatto et al., v.2007; 1 ♂, 2 ♀ ov, CCDB 3759, Ilhabela, Praia das Pedras Miúdas, 25.ii.2012; 1 ♂, CCDB 2103, São Sebastião, Praia do Segredo, colls. F. Mantelatto et al., xi.2005; 1 ♀ ov, CCDB 2723, São Sebastião, Praia do Segredo, coll. C. Schubart, 29.xi.2009.
Distribution. Western Atlantic— USA (Florida), Belize, Puerto Rico, Virgin Islands, Barbados, Trinidad and Tobago, Colombia, Venezuela, Brazil (Atol das Rocas, Fernando de Noronha, Trindade, Ceará, Paraíba, Pernambuco, Alagoas, Sergipe, Bahia, Espírito Santo, Rio de Janeiro, São Paulo) (Werding 1982; Veloso & Melo 1993; Werding et al. 2003; Rodríguez et al. 2005; Coelho et al. 2007; Ferreira & Melo 2016).
Remarks. The species is found on the intertidal region, under rocks, on calcareous algae and coral reefs (Haig 1956; Werding 1982; Veloso & Melo 1993). It is morphologically similar to Pachycheles biocellatus (Lockington, 1858), from the eastern Pacific, and Pachycheles meloi Ferreira & Tavares, 2017, endemic to the oceanic archipelago of Trindade and Martin Vaz, Brazil (Haig 1956; Ferreira & Tavares 2017). Sequence accession number (GenBank): CCDB 2103—16S (JF900726) (Miranda & Mantelatto 2016).