TANAIDACEA AND ISOPODA-TATTERSALL. 243 



of cephalic horns with secondary spines, by the short terminal horns on the abdomen, 

 also with secondary spines, and by the very long, slender and spinous antennae. Only 

 male specimens occur in the collection, and they were all obtained in deep water in the 

 Antarctic Ocean near the Ice Barrier. 



Genus DOLICHISCUS, Richardson. 



48. Dolichiscus meridionalis , Hodgson. 



Antarctiirus meridionalis, Hodgson, 1910, p. 43, pi. VI, fig. 2. 

 Dolichiscus meridionalis, Richardson, 1913, p. 17. 



Occurrence. — Station 314, 5 miles N. of Inaccessible Island, McMurdo Sound, 

 222-241 fathoms, bottom fauna, one adult male, 38 mm. 



Eemarks. — I suspect Dolichiscus pfefferi, Eichardson, will prove to be the adult 

 female of this species. Richardson had only a female specimen at her disposal, and 

 both Hodgson's single specimen and my own are males. The differences between the 

 two species may quite well be sexual. It should, however, be noted that there is no 

 trace in the above specimen of the long processes from the basal joints of the fourth 

 pair of thoracic legs, almost meeting in the centre, which Richardson gives as one of the 

 characters of the genus Dolichiscus. 



Genus NEASTACILLA, nov. 



Diagnosis. — Agreeing with the genus Astacilla, Cordiner, except that (1) the 

 second thoracic somite is fused with the head, and its lateral parts are not expanded 

 downwards and forwards to cover partially the mouth-organs ; (2) the abdomen is 

 unsegmented, all the segments being fused into one piece. Type, Astacilla falclandica, 

 Ohlin. 



An examination of the figures given in Sars' Crustacea of Norway to illustrate the 

 genus Astacilla will show that in this genus the second thoracic somite is, as in the 

 majority of Isopods, quite free from the cephalothorax and marked off distinctly by an 

 articulation. Moreover, its lateral parts are expanded downwards and forwards so as 

 partly to cover the oral area. Furthermore, Sars' figures show, and his description 

 states that in this genus the abdomen is composed of two somites. 



In his account of the " Challenger " Isopoda, Beddard describes a species, Astacilla 

 marionensis, in which the second thoracic somite is fused with the head and not 

 expanded laterally to cover partially the mouth-parts, but the abdomen is described as 

 composed of three segments, though these segments are not shown in Beddard's figure. 

 Vanhoffen has described a species, A. kerguelensis, which is very closely allied to, if not 

 identical with, Beddard's species ; and, in his figure, the abdomen is shown to be 

 composed of three segments, thus bearing out Beddard's description. These two species 

 are closely allied to Astacilla falclandica, Ohlin, but the composition of the pleon will 

 not allow them to be referred to my new genus. 



