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



to be almost invisible on a dorsal view ; the epiniera are articulated by a distinct suture 

 with the terga, and for about one-third of their length pass outwards approximately in the 

 same direction as the terga of the segments ; the rest of the epiniera is bent downwards 

 quite at right angles to the proximal region ; the upper (outer) margin is somewhat con- 

 cave ; the terminal segment of the abdomen is itself rather shorter than the foregoing, 

 but has a greatly elongated telson spine, rounded at the extremity ; it has no epimera, 

 the terminal appendages or uropoda being articulated at its extreme lateral margin. 



The antennules are short, with a four-jointed peduncle ; the two proximal joints are 

 short, the third very long, the fourth joint extremely small and rudimentary ; the 

 flagellum has four joints, and is not so long as the third joint of the peduncle. 



The antennae are nearly twice the length of the antennules ; the peduncle is five- 

 jointed, with three very short basal joints and two long distal joints ; the flagellum is 

 rather longer than the distal joint and has eight joints. 



The mandibles terminate in a pointed extremity ; the basal region is much broader 

 and projects on the inner side where it is denticulate. 



The maxillse as in other species appear to be absent. 



The maxillipedes resemble very closely the corresponding appendages of Anceus 

 bathybius, but the endopodite is shorter in proportion and does not project far along 

 the second joint of the palp. 



The OTpercvAiform jirst pair of thoracic appendages (PI. XVIII. fig. 10) again resemble 

 very closely those of Anceus bathybius, but differ from those of other species, for instance 

 those recently described by Sars from the Norwegian Expedition, 1 in having six well- 

 developed joints. 



The two basal joints are comparatively short, the third is greatly elongated, the 

 fourth and fifth are very short and subequal, whde the sixth joint is extremely minute. 

 The inner margin of the second, third, and fourth joints is fringed witli long plumose 

 hah's, which are absent on the two last joints. The penultimate joint is almost covered 

 with stout hairs on its inner half. 



The remaining thoracic appendages are similar to each other ; they are stout clawed 

 limbs. 



The penial process is double. 



The abdominal appendages are not so purely respiratory as in Anceus stygius, that is 

 to say, both endopodite and exopodite are fringed with long plumose hairs. 



The Praniza form of this species (fig. 9) is represented by a number of individuals 

 rather smaller than the males ; two large specimens have the characters of mature females, 

 the middle segments being tumid and swollen. A very considerable number of smaller 

 immature specimens are also contained in the Challenger collection; these may lie the Ian al 

 forms of the present species, or they may belong to the next species, Anceus tubevadosus. 



1 Loc. cit., p. 85. 



