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Show 1877.] CRUSTACEA, CHIEFLY FROM SOUTH AMERICA. 667 flexed backward on the sides, with the posterior margins angulate-excavate. Terminal segment of the tail about as broad as long, with the sides excavated ; upper surface flat, with a shallow depression on each side, and a small median pit near the base. Antennse with the flagellum much shorter than the last joint of the peduncle, with the first joint the shortest. Basal joint of the uropoda (viewed from above) oblong, terminal (apparent lateral) joint quite minute. Colour light grey. Length 10| lines. Hab. Nicaragua, S. Juan (Salle). (Coll. Brit. Mus.) This species is remarkable for its large size ; it is larger than any other species of the genus in the British-Museum collection. In the prominent anterior margin of the head, beneath which the antennse are partly concealed, it resembles the genus Pyrgoniscus, Kinahan, which, I m a y add, is wrongly referred by Dr. Kinahan to the Por-cellionidee, and belongs certainly to the Armadillidce, and is nearly allied to Cubaris. • Family ONISCID^E. Subfamily ONISCIN^E. P O R C E L L I O , Latreille. De Saussure (Me'm. Soc. Phys. et Hist. Nat. Geneve, xiv. pp.477, 480), has based the characters of his primary sections of this genus on the form of the segments of the body. These appear to m e at once so natural and characteristic, that I adopt them as subgeneric divisions. Subgenus P O R C E L L I O. Postero-lateral angles of all the segments of the body acute, and produced backward. PORCELLIO CAYENNENSIS, sp. n. (Plate LXVIII. fig. 2.) Moderately convex, with the segments somewhat laterally produced, and separated from one another toward the lateral margins, everywhere closely and finely granulated, with larger granules, not extending far toward the lateral margins on each segment. Head small, transverse-oblong, deeply encased in the first segment, strongly granulated, with the antero-lateral lobes very prominent, concave above, and subacute at the extremity. Eyes small. All the segments of the body with the antero-lateral angles rounded; the posterior margins excavated on the sides towards the postero-lateral angle, which is acute and produced backward; seventh segment with the posterior margin regularly excavate. Segments of the tail short, with the lateral portion angularly flexed backward, the laterally flexed portion in the third segment equalling one third the width of the segment; terminal segment somewhat T-shaped, longer than broad, subacute at the extremity, and produced beyond the extremity of the basal joint of the uropoda. Antennse wanting. Colour light-yellow and brown variegated. Length ^ inch, breadth | inch. Hab. Cayenne. In neither of the two specimens in the collection is the terminal |