ISOPODA. 109 



last segment of the body is semicircular, and exactly fills up the 

 emargination formed by the preceding one; the posterior appendages 

 are very small and entirely inferior. The antennae consist of nine 

 joints, the last four composing the stem. On each side is a de- 

 pressed tubercle representing one of the intermediate antennae; the 

 intervening space is raised. The branchiae are vesicular, imbricated, 

 and covered by laminae(l). 



Ligia, Fab. 



The stem of the lateral antennae composed of a great number of 

 small joints ; two very salient stylets divided at the end into two 

 branches, at the posterior extremity of the body. 



Ligia oceanica ; Oniscus oceanicus, L., Desmar., Consid., 

 XLIX, 3, 4, about an inch long, grey, with two large yellowish 

 spots on the back. The lateral antennae are less than half the 

 length of the body, and their stem consists of thirteen joints. 

 The stylets are as long as the tail. This animal is very com- 

 mon on the coast of France, where it is seen climbing up the 

 rocks, 8cc. If an attempt be made to capture it, it quickly 

 folds up its feet and lets itself fall. 



In the Ligia italica, Fab., the lateral antennae are nearly as 

 long as the body; the sixth joint, or the stem, is divided into 

 seventeen small ones. The stylets are much longer than the 

 tail. . 



Ligia muscorum; Oniscus hypnorum, Fab., Cuv., Journ. 



d'Hist. Nat. II, xxvi, 3, 4, 5; Oniscus agilis, Panz., Faun., Ins. 



Germ., Fascic. IX, xxiv. The lateral antennae shorter than the 



half of the body, and their stem composed of but ten small 



joints. The peduncle of the posterior stylets is furnished on 



the inner side with a tooth and seta. 



In others, all terrestrial, the lateral antennae consist at most of 



eight joints which gradually diminish in size towards the extremity, 



so that no one of them appears to be divided or compound. 



Here, the posterior appendages, or stylets, project beyond the last 

 segment. The body does not contract into a ball, or does it im- 

 perfectly. 



Philoscia, Lat. 

 The lateral antennae divided into eight parts and exposed at base; 



(1) Tylos armadillo, Lat., fig. in the pi. d'Hist. Nat. of the great work on 

 Egypt from the Mediterranean. 



