ISOPODA. 
41 
The second antenna differs in the proportion of its principal joints and flagellum, 
being 3‘7. 16'5. 21 "5. and 16 as against 5'5. 14’5. 19. 15. of the female on which 
o O 
the detailed description is based. The first of these joints as measured, the third 
really, is devoid of spines. 
About thirty specimens of both sexes were taken in Winter Quarters during the 
whole of our stay, all, but one, inside the 50-fathom line. 
Antarcturus hiemalis. 
(Plate VI., fig. 1.) 
Specific characters :— 
Cephalosome and first four segments of the mesosome each with a pair of stout spines forming a 
single row on each side of the middle line. 
Epimera with very prominent spines. 
Mesosome rounded posteriorly and having a median keel terminating in a spine, the third 
abdominal segment, which is fused with the urosome, having laterally a very stout backwardly curved 
spine. 
Long setae predominate. 
The entire body is marked all over with small arborescent chromatophores. 
The anterior border of the cephalosome is incurved, and close to this margin is a pair of 
very prominent horns curved forwards and outwards, these are provided with several 
very long setse. Behind this is another pair, much smaller but still prominent, and 
these also have long setae connected with them. Abreast of the interval between 
these two pair of horns lie the prominent and well-developed eyes. 
The first four segments of the mesosome are subequal in length, and each is 
provided with a pair of very prominent spines placed one behind the other on each 
side of the mid-dorsal line ; long setae are associated with these. These segments are 
covered with minute spines, but outside the longitudinal rows they become much more 
prominent, and while varying in size, form a distinct fringe along the posterior 
border of each segment, the remainder of which is more or less coarsely tuberculated. 
The epimera bears one very pronounced spine and other smaller ones. The larger 
ones are setose. 
The three posterior segments of the mesosome are minutely spinous, but as with 
the more anterior ones the spines are far better developed laterally and also form a 
strong postero-lateral fringe. The epimera are distinct from these segments and bear 
very prominent setose spines. 
The metasome shows distinctly three segments and the urosome, all of which 
are fused. The first segment has a very large setose epimeral spine, the second has 
only a stout tubercle, while the third has an extremely stout backwardly curved spine, 
its base being as broad as the segment bearing it. 
o o o 
The urosome is rounded posteriorly, scabrous, and having a well-developed 
median keel which terminates in a spinous blade a little in front of the extremity. The 
borders are fringed with long setse. 
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