Institute during the session of 1878.* See “Trans. N. Z. Inst.” Vol. XI., p. 230, et seq. As generic descriptions of Crustacea are not accessible to most of the readers of our “Transactions,” I have thought it advisable to supply these in all cases where the genera are new to this country. The various species are mentioned in the following order, viz., Schizopoda, Isopoda, Amphipoda, and Phyllopoda. Schizopoda. Fam. Mysidæ. Thorax covered by a carapace, which extends to the base of the ocular peduncles, and is produced into a rudimentary rostrum. Mouth situated near the base of the antennæ. Six pairs of thoracic feet, provided with a well-developed palp. Tail of five plates, forming a swimmeret, as in Macroura decapoda. Genus Mysis, Latreille. External antennæ beneath the eyes, bearing two terminal filaments. Internal antennæ beneath the external; first joint furnished with an elongated laminar appendage; two succeeding joints slender and cylindrical, terminated by a long, filiform, multi-articulate flagellum. Pedipalps two pairs, entirely pediform; first pair three-branched; second pair two-branched. Six pairs of thoracic feet, consisting each of two branches, decreasing in length from before backwards, and formed for swimming; last two pairs furnished with a flabelliform appendage. In the female these acquire a great development, and constitute two large semi-circular plates, folded below so as to form an oviferous pouch, in which the young pass through their first stage of development. Abdomen very slender, tapering, elongated, nearly cylindrical. 1.M. denticulata, G. M. Thomson, (Ann. & Mag. N.H., ser. V., Vol. VI., p. 1.) Fig. 1. Female.—Carapace ratt slender and short, with a short, triangular, acute rostrum. Peduncle of the internal (upper) antennæ extending to the extremity of the scale of the external antennæ; second joint very short; third the widest. Scale of external antennæ somewhat broad, with a tooth at the outer angle, and long ciliæ on its inner side, and at its extremity. Middle lamella of the tail entire, toothed on each side, and with two strong teeth at the apex. Lateral laminæ exceeding the central one; the inner narrow-lanceolate, acute, and furnished with long hairs on each side; the outer obtuse, with the apical half narrowing, ciliated only at the extremity and on the inside, and with a few stout teeth about the middle of its outer margin. Length .5 inch. Hab.—Dredged in Dunedin harbour, 4–5 fathoms.