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



Arcturus purpureas, F. E. Beddard (PI. XXIV. figs. 5-8). 



Arcturus purpureus, F. E. Beddard, Proc. Zool. Soc. Lond., 188G, ]>t. i. y. 109. 



A single specimen of this species was dredged in the North Atlantic at Station 23, 

 from a depth of 450 fathoms. 



I have named it purpureus on account of the purplish colour which appears to 

 characterise the species, and is very distinct in the spirit-preserved specimen. 



It is closely allied to Arcturus anna and to Arcturus cornutus, but differs sufficiently 

 from both to constitute the type of a new species. 



The extreme length of the specimen, which is a female, is 18 mm., the length of the 

 antennas 31 mm. 



On the head between the eyes are a pair of long forwardly curved spines ; the hinder 

 portion of the head is occupied by a rounded median convexity; at the anterolateral 

 margin of the head is a very short forwardly directed spine, beneath which the margin is 

 excavated by a semicircular notch. 



Of the first four thoracic segments the fourth is rather the shortest. Each of the 

 segments bears an outwardly directed spine on each side of the body corresponding to 

 the pair on the head, and of about equal length ; those on the fourth segment, although 

 broken, appeared to have been originally somewhat shorter; close to the lateral margin 

 of each segment, near to its junction with the epimeron. is another long spine pro- 

 jecting outwards and over the epimeron. The first segment differs from the succeeding 

 ones in having no separate epimeron, and its lateral margin has two spines instead of 

 one, of which the anterior is the longer ; they are both directed forwards as well as 

 outwards. The fourth thoracic segment has also a second spine, and its postero-lateral 

 margin inclined downwards and backwards as well as outwards. 



Of the three posterior thoracic segments the first is the largest, the two posterior being 

 equal in size ; the epimera of all three segments bears a spine directed outwards, and at 

 right angles to the longitudinal axis of the body ; that of the first of the three segments 

 is considerably the longest; this segment bears also a pair of spines upon I he tergum 

 continuous with those on the segments in front, and exactly overlying that on the 

 epimeron. 



The first three segments of the abdomen are separated by distinct sutures ; the firct 

 and the third of the segments have a pair of long lateral spines ; those of the third 

 segment mark the boundary between it and the caudal shield; the first abdominal 

 segment has a pair of short ventral spines placed on either side of the median ventral 

 line, and upon a ridge which forms the posterior margin of the segment ; anteriorly the 

 segment is bounded by a similar ridge, but without any distinct spines. 



The caudal shield is oval and convex, with a faintly marked, longitudinal carina which 

 terminates in a long spine; the lateral margins of the caudal shield are flattened and 



