38 THE VOYAGE OF H.M.S. CHALLENGER. 



the body are, as elsewhere, covered with .short spines, which are here as on the posterior 

 segment of the thorax hooked; the posterior region of the abdominal .shield, from the 

 articulation of the uropoda onwards, is smooth and entirely devoid of spines, with the 

 exception of the four terminal spines. 



The antennules are displayed in fig. 10 of PI. V.; they ((insist of a two-jointed 

 peduncle and a five or six-jointed flagellum; in the peduncle the proximal joint is 

 broader as well as shorter than the succeeding joint. 



The antenna} (fig. 9) are very much longer than the antennules, but not so long as 

 the body ; the proximal joints are short and subequal ; the two distal joints of the 

 peduncle are of great length, the last being slightly the longest ; the flagellum is shorter 

 than either of the two terminal joints of the peduncle ; it is composed of twenty or 

 more joints, of which the first is the longest. 



The mandibles terminate in a bifid masticatory process, each division of which is 

 again divided into two or three teeth ; the masticatory edge is also furnished with several 

 denticulated spines ; there is a stout molar process ; the palp is long and three-jointed, 

 the middle joint is rather the longest ; the terminal joint and the distal half of the 

 middle joint are beset with a single row of fine spines ; at the extremity of the distal 

 joint, which is somewhat curved, are four or five longish stiff hairs, which decrease 

 gradually in length from before backwards. 



One of the maxillipedes is represented in fig. 12 ; the palp is five-jointed, the joints 

 gradually decreasing in width towards the extremity ; the inner margin of the stipes is 

 furnished with two processes shown more highly magnified in fig. 13 ; they evidently 

 correspond to similar structures in other Isopods, especially in the Munnopsidse. 



The first pair of thoracic appendages are modified into prehensile limbs ; one of these 

 is displayed in fig. 14 of PI. V.; the proximal joint is long 'and rather stouter than the 

 succeeding joint, one margin is fringed with a row of hooked spines ; the following 

 joints are short, the second rather longer than«the third and fourth, which are subequal ; 

 the fifth joint is oval and rather swollen, the inner margin, against which the narrow 

 sixth joint rests, has a few slender spines. 



The remaining thoracic a/ppendages 1 are elongate, particularly the three posterior 

 pairs ; the proximal joints are furnished with several rows of spines ; the terminal joint 

 of each limb is short and bears along, curved, slender spine and a short slender bail- on the 

 inner side of the former ; this arrangement is, however, very different from the twosubequal 

 terminal claws that are found in the thoracic appendages of Munna and other genera. 



1 In the interior of several of the thoracic appendages, probably Lodged in tin- vascular channels, were oi caedonally 



a number of green bodies of varying form, which I take to be parasitic Algee. I am not aware thai the occurrence of 

 parasites of this class have been noted in the Isopoda, though parasitic [nfusorians (Anoplq cularu, Balbiani, 



Reciteil zool. Suisse, ii., 1885, p. 277), are known from the appendages of Asellus. The presence of green bodies pre- 

 sumably coloured by chlorophyll might lie useful in determining, in disputed cases, whetliei a given specimen really 

 came from the bottom or had been caught up by the dredge in the surface waters. 



