6 T. V. HODGSON. 



Second pair of antennae composed of five joints in both sexes. 



Cephalon of the male large at the base, and prolonged anteriorly to a narrow 



extremity. 

 Cephalon united to the first thoracic segment, leaving six segments well 



developed. 



Uropoda biramous, each branch composed of two joints. 

 The first gnathopods are dissimilar in the two sexes. In the male they are 



much enlarged, and the propodite is furnished with a process directed 



backwards, a thumb, which forms a chelate hand. 



This genus has been instituted for the reception of Paratanais dimorphus 

 Beddard (1), and P. antarcticus Hodgson (7), which, on account of their strongly 

 marked sexual dimorphism, a character they share with Heterotanais G. 0. Sars, and 

 other minor features, can no longer be included in any existing genus. 



NOTOTANAIS ANTARCTICUS. 



Paratanais antarcticus Hodgson (8), pp. 240 & 241. 

 Nototanais antarcticus Kichardson (1 2), pp. 2 & 3. 



Body rather slender, but differing in its proportions in the two sexes, being rather 

 longer in the female, notwithstanding the fact that the cephalosome is much longer in 

 the male than in the female. 



Male. The cephalosome is pyriform, long, narrowest anteriorly ; this border being 

 obtusely angulated, and having a well-marked conical projection laterally which is 

 occupied by the eye. This cephalosome is a little longer than the first four free 

 segments of the mesosome. 



The mesosome comprises six segments ; the first is very short, and the next three 

 progressively increase in length, the two following decrease, the last being nearly as 

 long as the third. 



The metasome is six-jointed, five of the segments being subequal in size, the last 

 is twice as long and rounded, bearing the biramous uropoda postero-laterally. 



Female. The cephalosome is shorter and more distinctly conical than pyriform, 

 and is not longer than the first three free thoracic segments. The proportions of these 

 segments are similar to those of the male, though they are longer, the length of the 

 mesosome in male and female being as 9 to 11. 



First antenna. That of the male comprises five joints, of which the first is longer 

 than the other four together, the proportion being as 6 to 4 ; the second is as long as 

 the two terminal ones, the third being by a very little the shortest of the series. 

 Except the penultimate all the joints bear a few long setae distally ; the terminal joint 

 has half-a-dozen or thereabouts. In the female this organ is tri-articulate, the first 

 joint being nearly twice the length of the other two together. There are a few long 

 setae distally and in the middle of the first joint. 



