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



short and subequal, with rounded lateral margins ; the dorsal surface of all these segments 

 has numerous tubercles similar to those upon the head, which become rather less numerous, 

 though they do not disappear, in the median line. The fourth thoracic segment is 

 separated by a considerable interval from the third, the interspace being occupied by 

 chitinous integument which is apparently not calcified ; this segment is tuberculate like 

 the others, but not quite to so great an extent ; its anterior margin is slightly concave in 

 the middle line, like the posterior margin of the head. The two following segments 

 differ from the anterior segment of the thorax in being perfectly smooth dorsally ; the 

 first of these segments is divided into right and left halves by a median longitudinal 

 furrow as in other species ; the sixth segment projects on either side beyond the terminal 

 border of the segment ; between this segment and the first segment of the abdomen is an 

 oval sclerite, which probably, as has been suggested by Dohrn, 1 represents the seventh 

 thoracic segment. On the ventral side these posterior (fifth and sixth) segments of the 

 thorax are as in other species uncalcified or incompletely calcified. 



The first five segments of the abdomen are subequal ; their lateral margins are 

 furnished with sickle-shaped cpimera, which are directed downwards, as in Anceus gigas, 

 and not outwards, as for instance in Anceus tuberculosus. The terminal segment of the 

 abdomen ends in a finely pointed extremity. 



The antennules have the ordinary structure ; the two basal joints are short and sub- 

 equal ; the third joint is as long as both together, but more slender, the fourth joint is 

 very minute ; the flagellum is four or five-jointed, and shorter than the peduncle. 



The antennse have a peduncle consisting of four joints ; the first two arc rather short 

 and subequal, the third longer, and the fourth longer still ; the distal joints have a few 

 fine hairs along the outer margin ; the flagellum is about as long as the last joint of the 

 peduncle, and has six joints ; it gradually tapers towards the extremity. 



The mandibles have the form depicted in fig. 1 1 ; the inner margin is extremely 

 prominent, and is bent with numerous crenulations. I am unable to describe the 

 maxillipedes as they were entirely concealed by the first pair of legs. 



The latter are very much like those of Anceus stygius described and figured by Sars, 

 and indeed like the majority of species ; they consist of a large basal joint, at the 

 extremity of which is a small oval joint ; at the distal extremity of this is a minute 

 tubercle which represents the third joint ; this description may be compared with that 

 of the same appendages in Anceus bathybius. The remaining thoracic appendages arc 

 subsimilar. The basal joint is stout and fringed along the inner margin with rows of 

 short spines, which are also found upon the more distal joints ; the three following joints 

 are moderately stout and gradually decrease in length ; the distal joint is as long as the 

 second joint but narrow, the short terminal joint bears a single claw ; a few slender hairs 

 are developed upon all the joints. 



1 Entwickelung mid Organisation von Praniza (Anceus) maxillaris, Zeitschr, f. wiss. Zool, Bd. xx., 1869. 



