8 THE VOYAGE OE H.M.S. CHALLENGER. 



been mentioned, wanting in Janira tristani; the possibility, however, that they are really 

 abortive must be borne in mind. I have indicated them in the figure as they were in two 

 small specimens (l mm. in length) from the same locality, which may possibly belong to 

 the same species. 



Station 135c, off Nightingale Island, Tristan da Cunha, October 17, 1873; hit. 

 37° 25' 30" S., long. 12° 28' 30" W.; 100 to 150 fathoms. 



Stenetrium, Haswell. 



Stenetrium, "W. A. Haswell, Proc. Linn. Soc. N.S.W., vol. v. p. 478. 



Mr. Haswell has described an Isopod which he regards as the type of a new genus, 

 Stenetrium, from Sydney Harbour ; his description refers to a single male example. 



A specimen which I describe here appears to be another representative of this same 

 genus but to belong to a distinct species from that described by Haswell ; I refer it to his 

 genus on account of the elongate flattened form of the body which is of uniform diameter 

 throughout, the narrow oblicmely placed eyes, the short biramose uropoda, and the large 

 chelse of the male. Mr. Haswell at first assigned this genus to the Tanaidae, and it 

 appears in his catalogue of Australian Crustacea (p. 308) as the type of a new subfamily, 

 Stenetrinse. More lately 1 Mr. Haswell dissents from his former conclusion and refers 

 Stenetrium to the Asellidse ; with this conclusion I entirely agree. 



In the Challenger specimen the posterior appendages of the thorax are in every case 

 broken off and lost, and as the general shape of the body is decidedly unlike that of the 

 Asellidse but much more like that of certain Munnopsidse, particularly Desmosoma," I 

 was at first inclined to assign the species to the Muunopskke. A careful comparison with 

 Haswell's figures 3 of his species appears to me to show that my own species is referable 

 to Haswell's genus Stenetrium, which is distinctly an Asellid and not a Munnopsid. 



The genus may perhaps be regarded, like Macrostylis and Ischnosoma, as in certain 

 respects transitional between the more typical Asellidas and the Munnopsidse. 



The occurrence of an Australian shallow-water genus in deep water, off the shores of 

 South America, is the more interesting as the two species are but little different. 



The characters of Stenetrium hasweUi necessitate a statement of the generic 

 definition, which is as follows : — 



"Body dorso-ventrally compressed ; abdomen short with all the segments fused into 

 ;i single piece. Head with a short rostrum ; segments of the thorax subequal. Antennae 

 inserted on to the anterior margin of the head, internal pair short, external pair long; both 

 with well developed Hagellum ; outer antenna) with a movable joint attached to third 



1 Proc. Linn. Soc. N.S. IV., vol. ix. p. 1010. 



2 Desmosoma is one of those species of which Professor Sars has kindly sent me a drawing in order to compare 

 with those collected by the Challenger; its general appearance, apart from the fact that it has no eyes, is strikingly 

 like that of Stenetrium haswelli. 



3 Proc. Linn. Soc. N.S.JV., vol. ix. pL li. 



