18'?5.] DURING THE VOYAGE OF H.M.S. 'CHALLENGER.' 923 



segments is a single median spine, one on either side of the median 

 line on each of the three succeeding segmenla The abdomen is 

 oval in shape, with an imniensel)' elongated telsou spine twice the 

 length of the abdomen itself. On either side are a pair of lateral 

 spines, the posterior being placed dorsal to tlie articulation of the 

 uropoda ; from the ventral surface of the caudal shield behind the 

 uropoda arises another spine, which is shorter in this species than in 

 the next to be described. The uropoda are 5-j(jinled. 

 Station 158, 1800 fathoms. 



2. ACANTHOCOPE ACUTISPINA, U. Sp. 



A single specimen, apparently a female, of this species was dredged 

 off the west coast of Patagonia. 



The specimen measures 5 rnillim. in length. 



It has the same general form as tiie last species ; but the three 

 poiterior thoracic segments, instead of being together double the 

 preceding thoracic segments, are only equal in length to the second, 

 third, and fourth of these segments. The upper surface of the body 

 in this species has not the median s, lines desciibed in Dolichurus 

 spinicauda. The epinieral spines are of comparatively much greater 

 length than in the last-described species, ai.d they, as well as the 

 general body-surface, are closely beset with short spines ; these 

 structures are also present in A. spinicauda, but apparently not to 

 so large an extent. 



The abdomen has the same general form as in the last species ; 

 but the terminal spine of the telson is much shorter, being only 

 about equal in length to the al)domen. 



The two first appendages of the thorax are shorter as well as 

 more slender than the sncceedin^. 



The uropoda are 3-jointed. 



Station 302, 1450 fathoms. 



Geographical and Bathymetrical Distribution. 



Although the Munnopsidae dredged by the ' Challenger ' were in 

 nearly every cases from very deep water, the genera of this family do 

 range into shallow water considerably above the 300-fathom line, 

 which is supposed with reason to represent approximately the 

 boundary line between the abyssal and shallow waters. Nearly all 

 the species described by Sars are from comparatively shallow water, 

 though several descend into water of 300 to 500 fathoms in depth, 

 e. g. Eurycope gigantea, 525 fathoms. In the southern hemisphere 

 only one species has been found to inhabit shallow water. A Mun- 

 nopsid was obtained on the shores of Kerguelen, which are so 

 productive in other Isopoda, notably in the genus Sero/is; this is a 

 species of the genus Ilyarachna which I have not at present deter- 

 mined with certainty. 



The majority of the deep-sea species were obtained in the vicinity 

 of land, for example, near to New Zealand and to the coast of South 

 America. In many instances stations situated at vast distances from 

 any land (such as Stations 157 and 158 between AustraHa and 



