Myzostoma armatae, new species, is an ectocommensal of Analcidometra armata (Pourtales) in the Bahamas and Jamaica, and of Davidaster discoidea (Carpenter) in Jamaica. Myzostoma attenuatum, new species, is a widespread ectocommensal of diverse Indo-Pacific comatulids. Myzostoma divisor, new species, is an Antarctic and sub-Antarctic ectocommensal of Promachocrinus kerguelensis Carpenter and of Notocrinus mortenseni John. The post-settlement ontogeny of M. divisor is documented by scanning electron microscopy