664 MR. E. J. MIERS ON A COLLECTION OF [June 19, 



tremity, with the posterior margin straight, transverse. The genus, 

 thus restricted, will correspond to the section /3 of Brandt, and § 2 

 of Milne-Edwards in the genus Armadillidium, and will include the 

 Armadillo vulgaris^ of Latreille. The genus Armadillidium will 

 then be restricted to section a of Brandt, and § 1 of Milne-Edwards 

 in the same genus ; while the A. officinalis, Dumeril, and allied 

 species will constitute a distinct genus, which I propose to designate 

 Orthonus ^ 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 tlie 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 middb 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. 



Orthonus \ gen. nov. 



Armadillo, Brandt, ^. c. p. 191 (1833) ; nee Latr. 

 Armadillo {§ I), M.-Edwards, Hist. Nat. Crust, iii. p. 178 (1840). 

 Posterior margins of all the segments straight. Lateral margins 

 never revolute. 



' Messrs. S. Bate and Westwood, in the 'British Sessile-eyed Crustacea,' also 

 use tlie name Armadillo for A. vulgaris. 



2 op&os, straight ; ovos, wood-louse. 



" The Armadillo inconspicmis, from New Zealand, described by me (Oat. New- 

 Zeal, Crust, p. 95, pi. ii. fig. 4, 1876) belongs to this genus, 



