REPORT ON THE ISOPODA. 
39 
The uropodct, are rudimentary ; each consists of a somewhat conical piece articulated to 
the abdominal shield by its broad end ; at the free extremity there are a number of long hairs, 
and a minute articulated scale which appears to me to represent the endopodite; in figs. 16 , 
17 of PI. V. the terminal portion of this appendage is shown more highly magnified. 
Station 149 k, off Christmas Harbour, Kerguelen, January 29, 1874; depth, 120 
fathoms. 
Ischnosoma, G. 0 . Sars. 
Ischnosoma, G. 0. Sars. Eeretning orn i Sommeren, 1S65, foretagen Zoologist Reise ved Kysteme af 
Cliristianias og Cliristiansands Stifter. Christiania, 1866, p. 34. 
The Challenger collection contains two fragments of Isopods, which appear to belong 
to this genus and to represent two new species of it, as well as a single complete specimen 
of another species. 
This genus was formerly regarded by Sars as belonging to the Munnopsidse, but it 
has since been removed by him to the family Asellidse. In his account of the Isopoda 
collected by the Norwegian Expedition, Dr. Sars has pointed out that although the 
general aspect of the Crustaceans belonging to this genus is not unlike that of the 
Munnopsidae, the absence of any modification into natatory organs of the three posterior 
pairs of thoracic appendages is opposed to their being placed in this family. The same 
is also the case with Macrostijlis. 
The genus is defined by Sars as follows : — 
Body elongate and narrow, broadest at first segment of thorax ; hinder part of 
segment four and anterior part of segment five firmly connected, and forming an hour- 
glass shaped portion which is nearly equal in length to half the body. Head small and 
rounded, eyes absent. The abdominal segment much longer than broad, constricted at the 
base, rather dilated towards the apex and obtusely rounded. Upper antennae projecting a 
little beyond the first joint of the peduncle of the lower antennae, six -jointed, the second 
joint narrow and elongated ; lower antennae slender, longer than the body, the flagellum 
about equalling the peduncle in length and composed of about nineteen joints. Feet of the 
first pair short and robust, subprehensile, the antepenultimate joint strongly dilated. Fol- 
lowing feet slender and elongated, similar to each other, six-jointed, the last joint forming 
a claw very elongate in the posterior three pairs of limbs. Caudal appendages simple. 
Sars has described two species of this genus, viz., Ischnosoma bispinosum and 
Ischnosoma quadrispinosum ; the former is distinguished by the presence of a spinous 
prolongation of the lateral margin of the first thoracic segment ; in Ischnosoma quadri- 
spinosum, the first and fourth thoracic segments are thus provided, and the uropoda are 
rudimentary. Two of the species to be described in the present Report are distinguished 
in the first place by their very large size as compared with the two northern representa- 
