THE CRUSTACEA OF NEAV JERSEY. 225 



mesosome, front sub-truncate, marginate, lateral lobes distinct, 

 median lobe obsolete, epistome vertical. Metasome not abruptly 

 contracted, terminal segment short and broad. Antennae com- 

 paratively small, with flagellum biarticulate or triarticulate. 

 Oral parts of similar structure to Oniscidse. Legs comparatively 

 short. Opercular plates of all pleopoda, or only of two anterior 

 pairs, provided with air-cavities. Copulative appendages about 

 as in Oniscidje. Uropoda short, not extending beyond limits of 

 last segment and epimeral plates of penultimate one. Young, 

 on leaving mother, all with seven segments of mesosome dis- 

 tinctly defined. 

 Genera about ten. 



Genus ARMADILLIDIUM Brandt and Ratzeburg. 



The Pill Bugs. 



Armadillidium (Brandt) Brandt and Ratzeburg, Med. Zool., II, 1830-34, p. 81. 



Type Arvtadillidiuni commutatiim (Brandt) Brandt and Ratzeburg, first 



species. 

 Armadillo (nee Brisson 1756) Latreille, Hist. Nat. Crust. Inest., VII, 1804, 



p. 47. Type Ariiiadillo vulgaris Latreille, first species. 



Body oblong or elliptical in form, very convex, and capable 

 of being rolled up into a perfect ball. Cephalon with front dis- 

 tinctly marginate, lateral lobes rounded and sharply defined at 

 base. Epistome vertical, forming above a triangular shield, 

 advancing more or less beyond frontal edge. Side plates of 

 first segment of mesosome large, securiform, not incised behind. 

 Metasome semicircular, with edges continuous throughout. 

 Last segment lamellar, quadrangular or triangular in form, not 

 extending beyond limits of epimeral plates of penultimate seg- 

 ment. Eyes distinct, lateral. Antennulse with terminal joint 

 but little produced. Antennae usually attains half body length, 

 penultimate peduncular joint scarcely longer than second, fla- 

 gellum biarticulate. Opercular plates of only first two pairs of 

 pleopoda with air-cavities. LTropoda very short, basal part 

 broad, lamellar, outer ramus spatulate, inner narrow, cylindric. 



15 MU 



