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



but the small lateral tubercle of the male has become developed into a long spine. The 

 third and fourth segments of the male have exactly the same spines, with the addition of 

 another spine which replaces the lateral tubercle of the second segment, and a short 

 median dorsal spine ; the female is much the same. On the second, third and fourth 

 segments there are in both sexes a single transverse row of longisli spines near to the 

 anterior margin of the segment. 



Each of the three posterior thoracic segments bears a ridge with a single row of long 

 spines arranged at equidistant intervals ; there are three pairs of spines, one pail 

 epimeral, and in the female several shorter ones in addition. 



The first abdominal segment has a single row of comparatively short backwardly- 

 curved spines ; on the second and third segments these spines become considerably 

 longer, especially the lateral spine on either side which marks the anterior extremity of 

 the caudal shield. 



The caudal shield in both sexes is covered with longisli curved spines ; just above 

 and near to the termination of its lateral margins are an extremely long pair of spines 

 directed outwards and slightly upwards. 



The antennules extend half way along the third joint of the antennas. 



The first three joints of the antennae, more particularly the third joint, are furnished 

 on the upper surface with spines ; there are four or five of these spines on the third joint. 

 The fourth and fifth joints are longer than the third joint ; they have no spines, but like 

 the preceding joints, are also beset with numerous fine long hairs ; the flagellum is 

 moderately short, barely half as long as the fifth joint, and consists of about seven rings. 



The proximal joints of the thoracic appendages (fig. 3-6) are furnished with sjiines. 



The uropoda are tuberculate in the male and covered with short curved spines in tin- 

 female. 



Station 147, December 30, 1873 ; lat. 46° 16' S., long. 48° 27' E. ; depth, 1600 fathoms; 

 bottom temperature, 34°'2 F. ; Diatom ooze. 



Arcturus abyssicola, F. E. Beddard (PI. XXI. figs. 5-8). 



Arcturus ahyssicola, F. E. Beddard, Proc. Zool. Soc. Lond., 1886, pt. i. p. 111. 



Of this species again only a single specimen was obtained by the Challenger ; the 

 specimen is unfortunately mutilated, the abdomen having been broken off and lost. The 

 species is interesting from the fact that it was dredged in water of 2385 fathoms, nearly 

 the greatest depth at which any genus of Isopods is known to live. In other resjjects 

 it is not remarkable. 



The head and thorax measure some 15 mm. in length, the antennas, which are of 

 great size, 42 mm. 



Of the first four thoracic segments the second and third are equal in size, and rather 



