REPORT ON THE ISOPODA. 133 



males as well as females among them, though I am bound to say that I did not discover 

 any decided evidence of a difference of sex, unless the elongation of the abdomen marks 

 the males in this species as it does in the genus Leptognathia. 1 This being the case, the 

 four-jointed antennules and antennae in both sexes will perhaps be considered to constitute 

 a sjeneric character. 



In no genus are these appendages four-jointed in both sexes, though frequently 

 (e.g., Leptognathia, Cryptocope) they are four-jointed in the female. Professor Sars, in 

 his Revision of the Tanaids, mentions that in Haplocope, Strongylura, and Anarthrura, 

 the antennules of the female are four-jointed, but he makes no statements respecting the 

 males of these genera. This present genus, however, cannot be confounded with either 

 of the three, since it possesses distinctly separate ocular lobes, which are wanting in the 

 genera above referred to. 



Bathytanais bathybrotes, F. E. Beddard (PL XVII. figs. 9-14). 



Paratanais bathybrotes, F. E. Eeddard, Proo. Zool. Soo. Lond., 1886, pt. i. p. 119. 



This species is represented by a single individual from the great depth of 2050 

 fathoms. Judging from the antennules it is a female, though there were no other marks 

 of sex to decide the point conclusively. The specimen measures about 4 mm. 



The general shape of the body is elongated and narrow as in other species of the 

 genus. The surface of the body appears to be perfectly smooth. 



The cephalothoraeic shield is about as long as the first two segments of the thorax, it 

 is narrower anteriorly than posteriorly, and projects as a wide, obtusely pointed, rostral 

 process. The ocular lobes are present though small and pointed anteriorly, they contain 

 an abundance of reddish-brown pigment, and the vitreous bodies of the eyes were also 

 plainly visible through the integument. This is one of the few deep-sea species in which 

 eyes are well developed. 



The first free segment of the thorax is rather shorter than the rest, which are subequal. 



The length of the abdomen is about one-fourth of the length of the entire body ; the 

 five proximal segments are short and subequal, the first alone being a trifle longer than 

 the rest ; the terminal segment of the abdomen is longer ; it is rounded and bent down 

 at the extremity. 



The antennules (fig. 11) have a very characteristic form ; the basal joint is as long as 

 the rest of the appendage, and is extremely wide and flattened, much more so than in any 

 other Tanaid known to me ; the following joint is short and wide, the third joint of the 

 peduncle is no longer but is narrower than the preceding ; the flagellum consists of a 

 single joint somewhat conical in form, the narrow end being the distal. At the extremity 



1 G. 0. Sars, Revision af Gruppen Isopoda, Chelifera, &c, lot. cit., p. 40. 



