REPORT ON THE ISOPODA. 43 



equal iu diameter; the three last joints are beset with hairs arranged in tufts or scattered 

 singly over the surface ; the filament is made up of from fifteen to seventeen joints, 

 which, like those of the anterior antennae, increase in length and diminish in width 

 towards the free extremity ; the inner side of each joint, just before the attachment of 

 the joint in front, has a tuft of fine hairs ; the anterior margin of the middle joints has a 

 series of short curved spines like those already described in Serolis paradoxa (ante, p. 35) ; 

 the antennae of the males possess a series of delicate lamellar processes (PL II. fig. 6) 

 arranged in a single line along the inner side of most of the joints, being absent only 

 from a few of the extreme distal and proximal joints ; these structures, which are very 

 probably sensory, take the form of oblong lamellae with rounded angles, those at the 

 anterior part of the joint are larger and somewhat fan shaped ; their surface is marked by 

 a series of grooves radiating outwards from the base of attachment. 



The mandibles (PI. II. figs. 12, 13) are markedly asymmetrical, as in other species. 



The maxillcB present no peculiarities. 



In the maxillipedes (fig. 10) the stipes and the lamina are not separated by a 

 suture ; both are covered with scattered hairs, and a row of finer hairs clothes the inner 

 margin of the latter ; at the summit of the terminal joint of the palp is a small 

 protuberance carrying three stoutish hairs similar to those upon this and the preceding 

 joint. 



The j^rs^ pair of ambulatory appendages are figured by Grube in his Monograph, but 

 the hairs on the inner side of the penultimate joint are not quite correctly shown ; the 

 longer spines (PL II. fig. 7) terminate in two flat lateral expansions, and the axis of the 

 spine is continued into the posterior and longer of the two. 



The second pair of ambulatory a.p)pendages of the male (PL II. fig. 8) are modified 

 in the usual way {ante,, p. 13). 



In the remaining thoracic appendages (fig. 9) the two first joints are subequal in 

 length ; the third joint is about half the length of the second, the fourth slightly longer, 

 the fifth shorter than the fourth, and approximately of the same size as the second ; the 

 terminal joint is more bent and hook-like in the last pair of appendages than in any of the 

 others. The second joint (in the males only) has a series of about fifteen tubercles close to 

 the inner margin ; the third, fourth, and fifth joints are furnished with numerous long and 

 slender hairs as well as stouter sword-like and serrated spines arranged in tufts in the 

 usual way ; the last pair of appendages in the male are distinguished from the rest by 

 a greater development of hairs upon the inner surface of the terminal joints ; this is an 

 approximation to the marked diS"erence that these appendages show in other species 

 {e.g., Serolis gracilis). In Serolis schythei, however, these hairs are not, as in the above- 

 mentioned species, in any way diflerent from those upon the rest of the ambulatory 

 limbs. 



The three anterior abdominal appendages are characterised by the absence of 



