34 
R. NORRIS WOLFBNDBN. 
than Ri ; fifth feet of three segments, last much smaller than proximal two, only basal 
with marginal teeth, end segment with three short outer and one long inner spine. 
6 a pair of fifth feet, the right very rudimentary and short, of three segments. 
(Polar Sea. Norway.) 
5. X. CRISTATUS. 
X. cristatus, Wolfenden, Jour. Mar. Biol. Assoc., 1904, p. 119. 
Size 5’Omm.; head triangular and 'with prominent crest, anterior antennae 
reaching to end of furca ; fifth feet of three segments, all densely spinulose, with two 
short apical spines. & not known. (West of Ireland.) 
G. X. SUBCRISTATUS. 
X. subcristatus, Wolfenden, Plankton Studies, Part II. (1906), p. 31. 
Size 7'0 mm. ; head with crest, abdomen very hirsute, fureal segments very short, 
anterior antennae reaching end of genital segment; fifth feet three segments, the distal 
long and tapering, with two short apical spines ; all these segments densely spinulose. 
$ not known. (South Polar Sea.) 
7. X. MAGNUS. 
X. magnus, Wolfenden, op. cit., p. 32. 
Size 8'8 mm. ; head rounded, not clearly separated from next segment ; fureal 
segments very short, anterior antennae reaching the genital segment; abdominal 
segments very hirsute ; fifth feet of three segments, very small ; all segments very 
spinulose, with two apical and two lateral spines on the last segment. $ not known. 
(South Polar Sea.) 
8. X. SIMPLEX. 
X. simplex, Wolfenden, op. cit., p. 30. 
Size 1'45 mm. ; whole surface of thoracic segments covered with fine prickles, 
anterior antennae very short, posterior antennae with Re nearly twice as long as Ri ; 
anterior foot jaws with only vermiform processes, posterior foot jaws with long, thin 
B 2 without bristles ; fifth feet very small, of common basal and two segments, the 
distal one very small, with two apical spines on the left and only one on the right foot. 
6 unknown. (West of Ireland.) 
9. X. CALAMINUS. 
X. calaminus, Wolfenden, op. cit., p. 34. 
Size 5'5 mm. ; fureal segments as broad as long, posterior antennae with rami of 
equal length ; anterior foot jaw with powerful toothed hook on fourth lobe, and two 
slenderer hooks on fifth lobe ; brush and vermiform processes ; posterior foot jaw short 
and stout, the bristles of the endopodite very peculiar and like quills, with broad 
chitin expansion with serrated edge ; fifth feet very small, of three segments; distal 
segment with short apical and two short marginal spines. (Bay of Biscay.) 
