90 THE VOYAGE OF IT. M.S. CHALLENGER. 



both sexes, the second segment has two pairs of short median ventral spines placed 

 between the appendages, one in front and one at the posterior margin of segment ; the 

 third, a very long spine placed relatively further backwards, behind the articulation of 

 appendages instead of in front, and another spine corresponding in position to the 

 anterior pair of the segment in front ; these are to be found in both sexes. The epimera 

 of the three posterior thoracic segments have a large lateral spine in both sexes, and a 

 shorter posterior spine behind the articulation of limbs. 



The three first abdominal segments are distinct ; the first has ventrally, near to the 

 middle line, two pairs of short spines, one behind the other. Dorsally the segments are 

 roughened and tuberculate, the tubercles being stronger in the female; the last 'free 

 abdominal segment has a lateral spine on either side, placed just on the boundary line 

 between it and the caudal shield ; this spine is completely absent in the male. 



The caudal shield terminates in a sharp median spine and in two lateral spines 

 considerably longer than the median one, which are curved upwards and directed 

 somewhat outwards ; the surface of the caudal shield is covered with rounded tubercles 

 in the male; in the female these tubercles on the side of the caudal shield are produced 

 into short spines, a pair of which, situated just in front of the lateral terminal spines, are 

 longer than the rest ; in the male specimen, to which the above description applies, one 

 of these additional spines was present. 



Two smaller male examples, one measuring 41 mm., the other 36 mm., in length, 

 presented certain differences from the adult male above described. The development of 

 spines was considerably less ; on the head only the anterior pair of spines were present, 

 and on the first three thoracic segments only two pairs of long spines, the median pair 

 being absent ; the fourth thoracic segment had only the lateral spines in one specimen 

 (the larger); in the other the dorsal pair were also present. In female examples of a 

 corresponding age and size the spines were in one or two instances 'somewhat Less 

 developed than in the more mature examples ; there was nevertheless no possibility of 

 confounding the sexes as regards the secondary character. 



The antennules (fig. 9) reach two-thirds of the way along the third joint of the antennas. 



The two basal joints of the antennse (fig. 10) are very short ; the third joint is nearly 

 three times the length of the two taken together ; the fourth and fifth joints are 3ubequal, 

 and each twice as long as the third joint; the fiagellum is rather more than half the 

 length of either of the distal joints. 



The thoracic appendages (figs. 5, 7) in the female have a few short spines on the 

 proximal joints along the posterior surface ; in the male (figs. 6, 8) it is only the three last 

 appendages which are thus provided. 



The uropoda (figs. 2, 4) are tuberculate. 



Station 146, off Marion Island, December 29, 1873, lat. 46° 46' S., long. 45' 31' E. ; 

 depth, 1375 fathoms ; bottom temperature, 35°"6 F. ; Globigerina ooze. 



