REPORT ON THE ISOPODA. 93 



Arcturus cornutus, F. E. Beddard (PI. XIX. figs. 6-12). 



Arcturus cornutus, F. E. Beddard, Proc. Zool. Soc. Lond., 1886, pt. i. p. 108. 



This species, also from the deep sea, bears some resemblance to Arcturus anna, but is 

 evidently a distinct species, as will be seen from the following description, which refers to 

 a single female example. 



The specimen measures 36 mm. in length ; the antennas measure 64 mm. 



The proportions therefore agree as nearly as possible with those of Arcturus anna. 



The margin of the head is excavated in front and dorsally, the lateral margin of 

 the head below in front of the eye is notched ; between the eyes are a pair of long 

 forwardly curved spines ; behind the eyes a pair of blunt tubercles. 



The first three thoracic segments are subequal and a little longer than the fourth. 

 The posterior portion of eacb of these is occupied by a ridge which is narrow dorsally, 

 but considerably wider laterally ; dorsally this ridge is cpiite smooth and even, but 

 laterally it is divided by an antero-posterior furrow into two principal convex protuber- 

 ances ; the largest of these eminences placed about half way between the dorsal median 

 line and the lateral margin of the tergum is furnished with a long spine ; there is also 

 another spine of equal length set upon the lateral margin of the tergum projecting over 

 the epimeron ; behind this on the fourth segment is another spine more slender but not 

 cpiite so long, springing from the lateral margin of the tergum and projecting backwards ; 

 there are indications of similar spines upon the anterior segments, but in no case are they 

 more than sharp points which, however, increase in length from before backwards ; on 

 the first thoracic segment the more dorsal of the two spines upon the tergum does not 

 accurately correspond in position to that upon the following segments ; it is placed 

 relatively behind and below them. The epimera of the second, third, and fourth segments 

 have a single spine near to their posterior margin ; the length of this spine increases 

 progressively from before backwards, in the second and third of those segments the 

 margin of the epimeron projects in front of the spine into a broadly conical process which 

 is not represented in the fourth segment. 



In front of the posterior tergal ridge, and close to the anterior margin of the segment, 

 is a pair of blunt tubercles united by a slight ridge. The first segment has in addition a 

 single tubercle placed in front again of this ridge, and j ust on the boundary line between 

 the head and the first thoracic segment. 



Of the three posterior thoracic segments the first is a trifle the longest. Each is 

 ridged ; the dorsal part of the ridge is narrow, straight in the first, concave backwards in 

 the two last of the segments ; laterally the ridge is widened out and bears on either side 

 a single long spine directed outwards and a little backwards. The epimera of these 

 segments are large, and each has a long spine, almost exactly underlying that upon the 

 tergum, directed outwards and rather more downwards ; the first of these segments has 



