REPORT ON THE ISOPODA. 59 



The caudal shield is almost hexagonal in outline: its lenoth in both the male and 

 female is about 11 mm.; it is therefore smaller in proportion than that in Serolis hromley- 

 ana; its breadth is about 12. mm. The uropoda are attached at about the commencement 

 of the posterior fourth. The median portion of the shield is slightly keeled, and bears two 

 spines one in front of the other, the posterior being the larger of the two. On either 

 side are two other short flat spines. The caudal shield of this species is very similar to 

 that of Serolis schythei, but it is not so distinctly carinate, and the anterior median spine 

 is flatter and not so large as in Sewlis schythei, while the posterior median and the 

 lateral spines are larger than in that species. 



Appendages. — The second pair of antennae are a little longer than the flrst pair, 

 lu the Jirst antenme the two basal joints are of about equal length, the third 

 joint is twice as long as either of the preceding ones, the fourth joint short, hardly 

 longer than the first joint of tlie filament ; the filament is composed of about twenty 

 joints. 



The second paiv ofantennce have the third, fourth, and fifth joints as usual covered on 

 the inferior surface with tufts of hairs in groups of three or four ; the filament has some 

 fifteen joints. 



The mandibles do not appear to difi'er from those of other species. 

 The_^rs^ maxilke consist as usual of a stout elongated lobe and small oval lobe, both 

 of which articulate with the cardo ; the smaller lobe is furnished on the free cutting edge 

 with a single spine as it is in Serolis paradoxa {cf. PI. V. fig. 14). 



The maxillipedcs are figured on PI. V. fig. 6 ; the suture between the lamina and 

 stipes is complete ; the palp of the mandible is abundantly furnished with setse, and the 

 second joint has on the inner side the small protuberance characteristic of all the deep- ' 

 sea species of the genus (a). 



The second p)air of thoracic app>endages differ from those of other species in that the 

 hairs which clothe the inner margin of the penultimate joint are very similar in form ; 

 several of these are shown on PI. Y. fig. 7 ; the longer hairs («) only difter from tlu- 

 shorter ones (6) by the proportions of their length and breadth. 



The third pair (fig. 8) are as usual modified into a prehensile organ in the male ; 

 the third, fourth, and fifth joints are covered on the inner side with a dense row 

 of hairs which are shown magnified in fig. 9, a' ; these hairs are clothed on the 

 distal half with fine branches, and they closely resemble the hairs that are found on 

 the second thoracic appendage of the males of Serolis convexa. The fifth joint is oval, 

 narrowing towards the upper extremity ; it possesses the peculiar spines characteristic 

 of this appendage ; they are narrow and cylindrical, and terminate in a long thread 

 which is given ofi' from the upper surface of the spine just before its termination 

 (fig. 9, b'). The sixth joint is divided by a suture into a small distal portion and a long 

 proximal portion. 



