ISOPODS OF NORTH AMERICA. 



478 



about one and a half times longer than the third. The flagellum is 

 composed of eleven articles. The second pair of antennae have the 

 first four articles short and nearly subequal, the first two being some- 

 what shorter than the last two. An antennal scale is articulated to the 

 third article. The fifth and sixth articles are long, the sixth being a 

 little longer than the fifth. The fifth article is 1 mm. in length; the 

 sixth is a little more than 1 mm. long. The flagellum is multi- 

 articulate, and 2 mm. long. The maxillipeds have a palp of five 

 articles. The palp of the mandibles is composed of three articles. 



The first segment of the thorax has the post-lateral lobe large and 

 produced, the antero-lateral lobe obsolete, with the epimeral lobe at the 

 antero-lateral angles. The second and 

 third segments have the antero- and 

 post-lateral lobes small, but produced 

 and conspicuous, the lateral margin 

 between them being straight; the 

 epimeron is in two lobes, and occu- 

 pies a position between the antero- 

 and post-lateral lobes in both seg- 

 ments. The fourth segment has the 

 antero- and post-lateral lobes small, 

 but produced and conspicuous; the 

 post-lateral lobe is smaller than the 

 antero-lateral lobe, while in the two 

 preceding segments the antero-lateral 

 lobe is the smaller one; the epimeron 

 of the fourth segment is a single lobe 

 between the antero- and post-lateral 

 lobes. In the fifth segment the antero- 

 lateral lobe is large and produced, the 

 post-lateral lobe minute, and almost 

 inconspicuous; the epimeron is a sin- 

 gle lobe between the two. The sixth 

 and seventh segments have the antero-lateral lobes large and promi- 

 nent, the post-lateral lobes obsolete, and the epimeron situated at the 

 post-lateral angles. 



The abdomen is composed of a single large segment, the post-lateral 

 angles of which are small but very acutely produced. The posterior 

 margin has a large median rounded lobe. The uropoda are not quite 

 as long as the abdomen. The peduncle is about one-third the length 

 of the terminal segment. The inner branch is one and a half times 

 longer than the peduncle. The outer branch is lost in both uropoda of 

 the specimen examined. 



The first pair of legs are prehensile, but not longer than the others. 

 The six following pairs are ambulatory, with bi-unguiculate dactyli. 



FIG. 528. JANIRA OCCIDENTALS (AFTER 

 WALKER), a, FIRST LEG. b, THIRD LEG. 



