38 
THE VOYAGE OF H.M.S. CHALLENGER. 
the body are, as elsewhere, covered with short spines, wdiich 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 consist 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 antennae (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 appendages 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 hair on the 
inner side of the former ; this arrangement is, however, very different from the two subequal 
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 the vascular channels, were occasionally 
a number of green bodies of varying form, which I take to be parasitic Algse. I am not aware that the occurrence of 
parasites of this class have been noted in the Isopoda, though parasitic Infusorians ( Anoploplirya cvrculans, Balbiani, 
Recueil zool. suisse, ii., 1885, p. 277), are known from the appendages of Asellus. The presence of green bodies pre- 
sumably coloured by chlorophyll might be useful in determining, in disputed cases, whether a given specimen really 
came from the bottom or had been caught up by the dredge in the surface waters. 
