1414 THE VOYAGE OF H.M.S. CHALLENGER. 



hairs, without terminal spine, by the exterior and interior rami of the uropoda being 

 equal in length, and by the minute, triangular telson." He gives the length as 

 " 26 mm.," as though he had seen and examined a specimen, since Guerin's measure- 

 ment is " long de neuf lignes." The hairy wrists of the second gnathopods and the 

 equal rami of the uropocls agree with Guerin's figures, but Guerin makes no mention of 

 these characters in his text, and the figures by themselves certainly cannot be trusted. 

 If all the particulars of Guerin's account were to be accepted, his species would be 

 unique, since he gives four joints to the mandibular palp, only five joints apiece to the 

 gnathopods and perseopods, and can find no joints at all in the maxillipeds. Whether 

 the southern specimens here described belong to Guerin's species or not, they certainly 

 bear a very striking resemblance to the northern species, Euthemisto libellula (Mandt), 

 in some of its stages of growth. 



Euthemisto thomsoni, n. n. (Pis. CLXXIV., CLXXV.). 



1879. Themisto antarctica, Thomson, Trans. New Zealand Inst., voL xi. p. 243, pi. xd. figs. 2, 3 



(non Dana). 

 1886. „ „ Thomson and Chilton, Trans. New Zealand Inst., vol. xviii. p. 151. 



Persson and Pleon carinate, the last three segments of the perseon and the first three 

 of the pleon having the hind margin produced into a strong dorsal tooth ; the perseon 

 broad at the centre, especially in the female ; the first three segments of the pleon 

 laterally ridged, with the postero-lateral angles produced into small acute points. 



Upper Antennae. — First joint of the peduncle longer than broad, the two following 

 very short ; the flagellum in the female consisting of a single joint, long, tapering, 

 sharply curved at the tip, with small spines and setules round the convex margin, the 

 concave margin rather deeply serrate till near the apex, a fringe of slender filaments 

 projecting from a parallel inner margin ; in the male the flagellum terminates in several 

 slender joints. 



Lower Antennae. — Third (first free) joint of the peduncle little longer than broad, 

 fourth considerably longer than the third, fifth longer than the two together ; flagellum 

 in the female consisting of one slender, tapering joint, considerably longer than the 

 peduncle ; in the male the flagellum has a long first joint followed by several short ones. 



The Mouth-Organs agree so closely in all their main features with those described 

 for Euthemisto gaudichaudii that it is unnecessary to do more than refer to the figures 

 on Plate CLXXV. 



First Gnathopods closely agreeing with those of Euthemisto gaudichaudii. 



Second Gnathopods differing little from those of Euthemisto gaudichaudii, unless in 

 having the process of the wrist longer, reaching nearly to the extremity of the hand. 



First Perseopods. — The armature and general structure of both the first and second 

 perseopods are similar to those in Euthemisto gaudichaudii, but in the particular specimen 



