The myicolid copepod Pseudomyicola spinosus is reported from 22 new hosts (pelecypods) in Bermuda and the West Indies, from 1 new host (a pelecypod) in Madagascar, and from an ascidian (Pyuridae) in Curaçao (probably an accidental association). P. spinosus is redescribed, based on specimens from Isognomon alatus in Bermuda. Among 316 P. spinosus from Bermuda, Puerto Rico, Jamaica, Barbados, Brazil, Senegal, Madagascar, and Jugoslavia the dimensions of the body and caudal ramus varied widely. The ornamentation of the anal segment showed four different conditions of spination, and sometimes included an extra long ventral setule on either or both sides. The specimens studied are regarded as one species, P. spinosus, without apparent subspecific differences. The following are considered as synonyms of P. spinosus: P. glaber Pearse, 1947, Myicola tageli Pearse, 1947, P. anomalocardiae Narchi, 1965, and P. mirabilis Humes, 1959.