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Show 664 MR. E. J. MIERS ON A COLLECTION OF [June 19, tremity, with the posterior margin straight, transverse. The thus restricted, will correspond to the section /3 of Brandt, and § 2 of Milne-Edwards in the genus Armadillidium, and will include the Armadillo vulgaris1 of Latreille. The genus Armadillidium will then be restricted to section a of Brandt, and § 1 of Milne-Eowards in the same genus; while the A. officinalis, Dumeril, and allied species will constitute a distinct genus, which I propose to designate Orthonus2, characterized by the straight posterior margins of the segments, which are never revolute. The following is a tabulated arrangement of the genera to which the species described in the present paper are referred :- I. ARMADILLIDIA. Armadillidia, Brandt, Bull. Soc. Nat. Mosc. vi. p. 184 (1833). Apical joint of the uropoda usually large, inserted at the apex of the basal joint. ARMADILLIDIUM, Brandt (section a), Bull. Soc. Nat. Mosc. vi. p. 185 (1833) ; Milne-Edwards (§ 1), Hist. Nat. Crust, iii. p. 181 (1840). Terminal segment triangular, acute at the extremity. ARMADILLO, Latr. (part), Hist. Nat. Crust, et Ins. vii. p. 47 (1804). Terminal segment quadrangular, truncate at the extremity. II. CuBARIDEA. Cubaridea, Brandt, Bull. Soc. Nat. Mosc. vi. p. 189 (1833). Apical joint of the uropoda very small, inserted in the middh of the inner lateral margin of the produced basal joint. CUBARIS, Brandt, Bull. Soc. Nat. Mosc. Hist. vi. p. 189 (1833). Armadillo (§ 2), Milne-Edwards, Hist. Nat. Crust, iii. p. 179 (1840). Posterior margins of the first two or three, or even of all the segments of the body with the posterior margins angulate-excavate on the sides; lateral margins often somewhat revolute. Terminal segment with the posterior margin straight. O R T H O N U S 3 , gen. nov. Armadillo, Brandt, I. c. p. 191 (1833) ; nee Latr. Armadillo (§ 1), M.-Edwards, Hist. Nat. Crust, iii. p. 178 (1840). Posterior margins of all the segments straight. Lateral margins never revolute. 1 Messrs. S. Bate and Westwood, in the ' British Sessile-eyed Crustacea,' also use the name Armadillo for A. vulgaris. 2 6p8vs, straight; ovos, wood-louse. 3 The Armadillo inconspicuus, from N e w Zealand, described by m e (Cat, JNew- Zeal. Crust, p. 95, pl. ii. fig. 4, 1876) belongs to this genus, |