238 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



tary. Second antennae of normal structure and moderate length, 

 seldom, exceeding half the length of the body. 



Mouth parts adapted for biting. Mandibles without palp. 

 Maxillipeds not completely covering the other mouth parts and 

 with terminal jaarts more or less reduced. 



Thorax composed of seven well defined quite similar segments, 

 the lateral parts of which are generally expanded to thin, forni- 

 cate plates. 



Abdomen composed of six well defined segments. 



Pleopods five pairs, which are respiratory in function ; the 

 inner plate being of very delicate spongey structure whereas 

 the outer is more strongly chitinized and covers the inner like 

 an operculum. Air cavities are sometimes present in this oper- 

 culum. Uropods biramous, with rami uniarticulate. 



Oniscus asellus Linnaeus. 



Fig. 76. Oniscus asellus. 



1818. Oniscus aiTinis, Say, Jour. Acad. Nat. Sci. Phila., vol. 

 I, p. 430. 



1841. Oniscus asellus, Gould, Invert., Mass., p. 336. 



1899. Oniscus asellus, Sars, Crust. Norway, vol. 2, p. 171, 

 P- 75- 



1905. Oniscus asellus, Richardson, Bull. U. S. Nat. Mus., 



No. 54, p. 600. 



