108 THE VOYAGE OF H.M.S. CHALLENGER. 



form characteristic of this genus, it terminates in an elongated obtusely-pointed upturned 

 extremity ; on either side above the middle of its extent is a very prominent hooked 

 tubercle curved backwards ; the rest of its surface is smooth and free from tubercles. 



The antennules are as usual very short and reach to the end of the second joint of 

 the antennae ; the proximal joint is broad and stout and has a strong lateral ridge. 



The antenna? are as long as the head and six anterior thoracic segments. The first joint 

 is extremely minute, the second much longer, the third nearly twice the length of the second ; 

 the fourth nearly twice the length of the third; the fifth joint is rather shorter than the 

 fourth. The flagellum is short, and consists of three joints which decrease progressively 

 in length, the first being much the longest. The antennas appear to be without any hairs. 



The four anterior thoracic appendages are all similar to each other, and increase 

 progressively in length. 



The three posterior pairs are more or less similar to each other, and differ principally 

 from the anterior thoracic appendages in the shortness of the distal joints in the absence 

 of hairs and in the termination of the limbs in two claws ; the distal joints are roughened 

 by the presence of numerous minute tubercles. 



The uropoda are comparatively smooth. 



Two individuals, of which the largest measures 10 mm., were dredged in shallow water 

 off Kerguelen ; these specimens are to be distinguished from the ones described above by 

 their intensely dark colour, which is owing to the presence of numerous pigment granules. 

 In other respects they agree so closely that I cannot see any reason for distinguishing 

 them by a different specific name. 



Marion Island, 100 fathoms. 



Kerguelen, Betsy Cove, surface and shallow water. 



Arcturides, Studer. 



Arcturides, Studer, Sitzungsb. d. ges. naturf. Freunde, Berlin, April 1882, p. 57. 



This genus was founded by Studer for a small Arcturid dredged in shallow water 

 at Kerguelen, by the German exploring ship " Gazelle ; " it appears to form an inter- 

 mediate type between Arcturus and Idothetx ; its general aspect is that of the former 

 genus, while the similarity of all the thoracic hmbs is a characteristic of Idothea. 



Arcturides cornutus, Studer. 



Arcturus cornutus, Studer, loc. cit. 



A number of specimens of this species were dredged in comparatively deep water, 

 off Marion Island. Its vertical and horizontal range are therefore extended by the 

 explorations of the Challenger. 



