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



strongly toothed on tlie free margins, and a stout two-jointed palp, the first and largest 

 joint of which bears several long setse on each margin, the last joint armed with several 

 unequal curved claws ; a small branchial plate is attached to the base of the limb/ First 

 pair of feet in the female five-jointed, slender, and bearing at the base a narrow semi- 

 circular and somewhat lobate branchial palp, the last joint provided with three subequal 

 long and slender terminal claws ; in the male the limb is much stronger, and bears three 

 long, curved, and densely ciliated terminal setse. Second pair of feet rudimentary, two- 

 jointed, bearing two unequal apical setae, one of which is of moderate length, the other 

 several times the length of the entire limb. Postabdominal laminae short and wide, 

 rounded, and armed with numerous curved marginal claws, decreasing regularly in length 

 from the apex. Eyes w^anting. Copulative organ of the male double, not very complex 

 in structure, consisting apparently of a compressed tubular organ, divided into two 

 terminal, slightly-toothed, and setiferous lips, and enclosing an eff'erent duct. 



Three species of Halocypris have been recognised amongst the proceeds of the 

 Challenger tow-net gatherings. Of these Halocypris atlantica, Lubbock, is by far the 

 most abundant ; Halocypris brevirostris, Dana, also occurred not unfrequently ; and 

 another species, apparently undescribed, Halocypris imhricata (mihi), was met with only 

 seldom. 



1. Halocypris atlantica, Lubbock (PI. XL. figs. 1-15, and PI. XLL figs. 11, 12). 



Halocypris aifZ'.TO^zM, Lubbock, Trans. Entom. Soc, vol. ir., 1856, p. 28, pi. xii. figs. 1-8. 

 (?) Halocypris, sp. Clans, Ueber die Geschleohtsdifferenzen von Halocypris (Zeitschr. f. Wissenscb. 

 Zool., Bd. XV., 4 Heft, 1865). 



Carapace of the female (PL XL. figs. 1, 2), seen from the side, oblong, rather higher 

 behind than in front ; ^ anterior extremity produced at the dorsal angle into a subacute, 

 hood-shaped beak, below which is a deep notch, whence the margin rounds off into a full 

 curve continuous with that of ventral surface, the jjosterior extremity is rounded ofi" 

 below at its junction with the ventral margin, indented above the middle, and produced 

 upwards so as to join the dorsal margin almost at a right angle ; the dorsal margin in its 

 general direction is straight, but shows more or less sinuation ; ventral margin gently con- 

 vex ; the height of the shell is equal to more than half its length. Seen from above, the 

 outline is subovate, or tending to the shape of a hexagon with rounded angles, about 

 twice as long as broad ; lateral margins subparallel, converging to an acuminate point 

 behind, but in front forming a broadly rounded or subtruncate anterior extremity. Sur- 

 face of the shell marked with numerous closely-set, u-regularly-concentric striae, the 



1 Sars makes no mention of a branchial plate in connection witli the first maxilla, but assigns one to the second 

 maxilla, and a single branchial filament to the mandible paljj. These are the most important points of divergence 

 between the observations of Sars on Conchcecia, and those here given on Halocypris. 



^ The shape, as remarked by Sir John Liibbock, is not unlike that of the capital letter D. 



