SUMMARY.1 An account is given of the external and internal anatomy of a new species of the aberrant Copepod genus,Ophioica, occurring within the Ophiuroid,Ophiacantha imago(Lyman).2 Specimens of ovigerous and non‐ovigerous females, with their attached males, were examined.3 The body of the adult female is unsegmented and possesses several pairs of serpentine processes. Three such pairs are present in the non‐ovigerous female and four pairs in the ovigerous female. There are also processes which arise dorso‐laterally. The abdomen is distinct only in the ovigerous female.4 The internal organs of the female are gut and reproductive organs. The former can be divided into fore‐and mid‐gut, the latter much branched. If a hind‐gut is present it cannot be differentiated from the mid‐gut. In the ovigerous female the ovaries are paired and the genital openings are probably at the tip of the abdomen.5 The male is attached to the ventral side of the female, but only the male attached to the non‐ovigerous female was fully developed. It is also unsegmented, with a tapering abdomen and a pair of serpentine lateral processes. The internal organs are again gut and reproductive organs only and the genital openings appear to be at the tip of the abdomen. In the male attached to the ovigerous female the internal organs had practically disappeared.6 It was not possible to determine the process of transference of the spermatophores from the male to the female. It is probable that the genital openings are only perforated at maturity in both sexes.7 The ovigerous female carried eight egg‐masses, pressed under the ventral surface of the body and enclosed within a ‘brood‐pouch’ of host‐tissue.8 Certain points in the biology of these parasites, consequent upon their enclosure within