24 R. NOERIS WOLFENDEN. 



First feet Ri=. 1, Re= 3 ; no Se on Re 1, and very short Se on Re 2. 



Second feet Ri = 2, .Re = 3. 



Third and fourth feet Ri and Re ^. 



Fifth, each of three segments, two basal, each short and comparatively thick, 

 terminal segment longer and thinner, prolonged, with a stout curved hook with short 

 bristles on the upper margin and an external marginal thin and short bristle. 



The male is rather smaller than the female, the abdomen has five segments, the 

 mouth organs are as in the female, but the fifth feet are transformed into clasping 

 organs, that, of the right side of four segments, the left of five. The second and 

 third segments of the left are elongated, the distal segment short and broadened 

 out, the distal extremity ending in a spine, and at the opposite side a short knob 

 process, apparently without marginal hairs. 



The right foot with short broad second basal, and two distal very elongated and 

 thin segments, with a long thin sickle-shaped process at the end, which appears to be 

 a continuation only of the joint above it, and though forming an elbow, does not 

 articulate. 



In the general structure this small Copepod bears great resemblance to the 

 species Stephus antarcticum, which, however, is twice as large ; the fifth feet in the 

 female as well as the male are different, and the two species are therefore quite distinct. 



STEPHUS ANTARCTICUM. 

 (Plate V., figs. 4, 5, 6, 7, 8.) 



9 1'85-2'0 mm. long, cephalothorax about three times as long as abdomen, and 

 in its broadest part distal of the middle line one-third as broad as long. Head evenly 

 rounded, a little produced in front, but without trace of rostrum, a weak line indicating 

 its division from the first thoracic segment. Last two segments of the thorax im- 

 perfectly divided, and last segment a little unsymmetrical ; on the right side a little 

 longer than on the left, produced into a round-ended margin, on the left side more 

 acutely pointed, which is most marked in lateral view. Abdomen of four segments 

 respectively proportioned: genital segment, 2:3 and anal as 20:13:8:8; furcal 

 segments as long as the anal, and as broad as long. Genital segment laterally swollen 

 in the upper part (genital protuberances) and again slightly swollen laterally in its lower 

 part, with on each side a bunch of rather long spines, none dorsally. Furca with four 

 tail setae on each side, outer margins haired and with, on each side, a short lateral 

 spine instead of the usual bristle, and on the ventral side a very short accessory 

 bristle. Of the tail bristles, the two middle ones are much the longest and thickest, 

 and those of the right side more so than those of the left. 



Anterior antennae reach in both sexes to about the end of the second abdominal 

 segment, having twenty-four segments, the eighth and ninth coalesced. In the posterior 

 antennae the exopodite is longer than the endopodite. The mandibles with branches 



