ISOPODA. 41 



The second antenna differs in the proportion of its principal joints and flagellum, 

 being 37. 16'5. 21'5. and 16 as against 5'5. 14'5. 19. 15. of the female on which 

 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 mesosorne 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 setse predominate. 



The entire body is marked all over with small arborescent chrornatophores. 

 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 setae. 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. 



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 setae. 



VOL. V. Jf 



