1388 THE VOYAGE OF H.M.S. CHALLENGER. 



Hyperia dysschistus, n. sp. (PI. CLXVIL). 



In this compact little species, the sixth and seventh segments of the perseon are 

 distinct, but the first five segments, though more or less faintly marked, do not appear 

 to be separated except in the vicinity of the side-plates ; the body is large as compared 

 with the limbs ; postero-lateral angles of the first three pleon-segments squared. 



Upper Antennse. — In the male (no doubt not adult) specimen, the peduncle consists 

 of one joint broader than long, the flagellum of one thick joint, twice as long as the 

 peduncle, at first tapering rapidly, and at the end of the tapering portion carrying six or 

 eight filaments, the apical part of the joint not slender or tapering, with an indication at 

 the rounded end of a minute second joint. In the female these antennse were much 

 more slender, tapering from the base to the acute apex, the distal part of the flagellum- 

 joint carrying a series of four setules, and its tip being furnished with two which are 

 longer than those on the side. 



Lower Antennas in the male not so thick as the upper, with only two joints 

 distinguishable, the second much longer than the first, thick, with a blunt apex ; in the 

 female much smaller, tapering to an almost acute apex, with two minute setules side by 

 side upon it. 



Epistome deeper and broader than the Upper Lip; the latter with a rather deep 

 oblique distal incision, making it as usual unequally bilobed. 



Mandibles of the usual character, the molar tubercle very large, the palp not so long- 

 as the trunk, with its three joints but faintly separated, a character showing that the 

 specimen was not fully adult. The mandibles in the female resembled those of the male, 

 except in being without the palp. 



First Maxillas. — The outer plate appeared as usual triangular when seen in connection 

 with the surface of the palp, but the distal margin with its row of unequal spines was 

 seen to be far from acute, when the surface of the plate was seen and the palp turned 

 edgewise. It is not easy to say whether there is any substantial difference either in the 

 spines themselves or in their arrangement in the different species. There would seem to 

 be some specific variation in the armature of the palp, but it is all of a minute order 

 difficult to describe and not always easy to observe ; in the present sjiecies the palp has 

 a single comparatively large spine-tooth at the inner apex, the distal margin being cut 

 into very slender sharp teeth, the series of which is continued some little way down 

 the convex outer margin. 



Second Maxillas. — The outer plate longer than the inner, though not so much so as 

 might be inferred from the figure mx.2, where the inner plate is foreshortened; in the 

 lithographing all the spinules are given of equal thickness, but two or three of the apical 

 spinules on each of the plates are in reality more spine-like than the rest. 



Maxillipeds. — The inner plate as seen in profile almost triangular, beset with long 



