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



trimk, two segments of wkieli are partly exposed behind tlie posterior emargination. 

 The anterior third part of the carapace is marked ofl" by a well-defined and rather deep 

 cervical sulcus, and terminated with an evenly-arched frontal margin. The antero-lateral 

 corners are but very slightly produced, and obtuse-angled. 



The tail is about twice as long as the carapace, and very slender, cylindrical, tapering 

 scarcely at all posteriorly, with the last segment much longer than the others. 



The ocular plates are comparatively broad, and quite plane, extending horizontally 

 in front of the carapace, and occupying nearly the whole breadth of the frontal margin. 

 They are obtusely truncate in front, and separated in the middle by a very small cleft. 

 The outer edge is slightly arcuate, and finely serrate along its anterior part, forming, 

 together with the anterior edge, an obtuse angle. As in the other species, no trace of 

 pigment or any visual elements can be detected ; but the optic nerve forms, within the 

 ocular plate, a ramification exactly similar to that described by the author in Fseitdomma 

 roseum. 



The antennular peduncle exhibits the usual form, being very short and thick, with 

 the last joint longer than the two others taken together. The male appendage is some- 

 what shorter than the last joint of the peduncle, and provided with the usual dense 

 bunch of hairs. 



The antennal scale (fig. 2) is about twice as long as the antennular peduncle, and of 

 an oblong form, about three times as long as broad. The apex is somewhat obliquely 

 truncate, though not nearly to such an extent as in the other known species, and the inner 

 corner therefore appears but slightly produced and bluntly rounded. The denticle of the 

 outer corner is rather strong, and placed much nearer to the apex of the scale than in any 

 of the other species. 



The endopodal parts of the legs, as also the terminal parts of the antennular and 

 antennal flagella, were broken off in all the specimens preserved. 



The telson (fig. 3) has about the length of the last caudal segment, and exhibits a 

 somewhat linguiform shape, being broadest at the base and tapering regularly toward the 

 apex, which is broadly rounded or almost truncate. The lateral edges are armed in their 

 outer part, on either side, with about eight very small denticles, and from the apical edge 

 issue ten much larger denticles, increasing in size inwards, and assuming the character of 

 strong spines ; moreover, a small tubercle occurs in the middle, as in the other species, 

 bearing two very delicate and diverging bristles. As regards form, the telson of the 

 present species bears most similarity to Pseudomma truncatum, Smith, but in that species 

 the number of the terminal spines is much less, viz., not over six. Pseudomma ajfine, 

 G. 0. Sars, on the other hand, has no less than twelve terminal spines, but in that form 

 the apical edge is not distinctly defined from the lateral ones. 



The uropoda exhibit the usual form, and have, the auditory apparatus within the base 

 of the inner plates distinctly developed. 



