222 CLASS CRUSTACEA. 



Anthura, Leach y 



Have the body vermiform, and the antennce scarcely as long 

 as the head, with four articulations. The leaflets of the 

 posterior fins form by their disposition and approximation a 

 sort of capsule. 



The anterior feet are terminated by a monodactylous pin- 

 cer. 



In the fourth section, Idoteides, Leach, the antennae are 

 also four in number, but on the same horizontal and trans- 

 verse line. The lateral are terminated by a stem, finishing 

 in a point, gradually gi'owing more slender, and pluri-articu- 

 lated. The intennediate are short, filiform, or a little thicker 

 towards the end, of four articulations, none of which is di- 

 vided. The composition of the mouth is the same as in the 

 preceding sections. The gills are in the form of bladders, 

 (white in the majority) susceptible of being swelled to serve for 

 swimming, and covered by two laminae, or valvules, of the last 

 segment, adhering laterally to its sides, longitudinal, biarticu- 

 late, and opening in the middle by a straight line, like two 

 shutters. The tail is formed of three segments, the last of 

 which is much larger, without appendages at the end, or 

 lateral fins. 



Idotea, Fab., 



Have all the feet strongly unguiculated, identical ; the body 

 oval, or simply oblong, and the lateral antennae shorter than 

 one half of the body. Oniscus eniomon, Lin. 



Stenosoma, Leach, 



Differ only in the linear form of the body, and the length 

 of the antennae exceeding the half of that of the body. {Ste- 

 nosoma lineare, Leach.) 



