1886.] DURING THE VOYAGE OF H.M.S. ' CHALLENGKR.' 107 



individual measures about 9 milliin. The first four thoracic segments 

 are subequal in length ; each is ridged posteriorly, the ridge widening 

 out laterally to occupy the whole of the segment, it is covered with 

 fine granulations ; in the fourth segment the ridge is higher than in 

 the preceding segments ; anteriorly between the ridge and the 

 anterior margin of tlie segment is a shorter ridge, likewise covered 

 with numerous minute tubercles ; on the first thoracic segment is a 

 third ridge ; of the three posterior segments the first is the longest ; 

 on each is a posterior ridge-like elevation beset with numerous 

 tubercles. The abdominal shield is oval, tapering towards its extremity, 

 which is slightly upturned; like the thorax, it is tuherculate. The 

 proximal joints of the antennae and of all the thoracic limbs are beset 

 with tubercles. 



Station 169 ; 700 fathoms. 



2. Arcturus anna, n. sp. 



This single specimen of this large species measures 37 millim. ; 

 the antennae are nearly twice the length of the body. The head is 

 excavated in front ; the antero-lateral margin of the head is notched 

 ventrally. The first four segments of the thorax are subequal ; each 

 is traversed by a ridge, which dorsally is narrow and only occupies 

 the posterior portion of the segment, laterally it is widened out and 

 occupies the whole of the segment ; in front is another shorter ridge, 

 which does not reach the lateral region of the segment ; at the extreme 

 lateral margin is a stout spine, inclined nearly at right angles to the 

 longitudinal axis, which overlies the epimeron ; behind are one or 

 two shorter spines along the postero-lateral border of the tergum. 

 The epimera, which are short, are likewise furnished with one or two 

 short spines ; these are only conspicuously developed upon the last two 

 of the segments, especially upon the last, where one of the spines 

 equals in length the tergal spine which it directly underlies. Of the 

 three posterior segments the first is decidedly the largest ; they are 

 ridged like the anterior segments, the ridge widening out laterally ; 

 each segment has a short lateral spine corresponding to those on the 

 anterior segments ; the epimera are also furnished with a stout spine, 

 that of the fifth segment with an additional spine directed forwards. 

 There are two completely free abdominal segments, the third being 

 to a large extent fused with the abdominal shield ; on the ventral 

 side of the first abdominal segment is a short spine on either side 

 anteriorly and another pair of longer spines posteriorly ; this segment 

 as well as the next has a short lateral spine ; the third abdominal 

 segment has on either side a long curved spine at the postero-lateral 

 margin. The abdominal shiel 1 has a central convexUy occupying 

 nearly the whole of its extent and bordered by a flattened rim, which 

 is serrated, and terminates posteriorly in a pair of pointed processes 

 projecting behind the central area, which terminates posteriorly in a 

 short pointed spine. The thoracic limbs of the second, third, and 

 fourth pairs have one or two longish spines on the three proximal 

 joints. 



Station 320 ; 600 fathoms. 



