that, as it was not possible to ascertain whether the ordinary form of _S. rutilum_ was hermaphrodite or female, so it must remain doubtful whether the parasites are males or complemental males; but the former, I think, is most probable. [=TT= SUB-CARINÂ PRESENTE.] 4. SCALPELLUM ROSTRATUM. Pl. VI, fig. 7. _S. (Herm.) valvis 15: rostro permagno: laterum paribus quatuor: pari superiore pentagono._ (Herm.) Capitulum with 15 valves: rostrum very large: four pair of latera; upper latera pentagonal. Mandibles with four teeth; maxillæ with the inferior angle prominent. _Complemental Male_, attached between the mouth and adductor scutorum muscle; pedunculated; capitulum bearing a pair of elongated scuta and a rudimentary carina; mouth and cirri prehensile. Philippine Archipelago; Island of Bantayan. Attached to a horny coralline: 20 fathoms. Mus. Cuming. HERMAPHRODITE. _Capitulum_, with the upper part narrow and produced. _Valves_, 15 in number, placed close together, clouded pale red, covered with membrane, which is thickly clothed with minute points. _Scuta_ rather small, oval, with the upper end pointed; rather convex; basal and lateral margins blending into each other; the upper produced portion above the umbo is small; there is a deep pit for the adductor muscle, and there is a fold on the occludent margin in the usual position; occludent margin not straight. _Terga_ large, one third of their own length longer than the scuta; fat, sub-triangular; the three margins are not quite straight; the carinal margin projects a little above the apex of the carina, and the scutal margin is excised to fit the upper part of the scuta. _Carina_ bowed, internally deeply concave; upper portion above the umbo, about one fourth of the total length, extending between the terga for two thirds of their length, up to the slight prominences on their carinal margins: a ridge separates, on each side, the parietes from the tectum. _Rostrum_ (fig. 7 _a_) unusually large, about two thirds of the length of the scuta, and twice as long as the rostral pair of latera; internally concave, externally carinated; outline of the upper portion acutely triangular, of the lower portion rounded; umbo seated at the upper end. _Upper Latera_ pentagonal, with the apex rounded. _Rostral Latera_ flat, four-sided, with the basal margin the longest, and the baso-carinal angle produced. _Infra-median Latera_ nearly equalling in area the upper latera; not descending so low down as the rostral and carinal latera; outline of lower half semi-oval, of upper half rectangular. _Carinal Latera_ flat, four-sided, with the basal margin the longest, and slightly protuberant; baso-rostral angle produced; whole valve larger than the rostral latus, but closely resembling it in form.