J. M. Thomson. 
38 
The natatory legs, except for the second and fifth, are armed as in 
the female and the seta on the fourth right coxa is normal, not expanded 
as a spine. Second pair of legs are asymmetrical, being similar to the female 
except that the left endopod has the proximal inner seta of the terminal 
segment modified into a stout spur. Fifth legs are distinctly asymmetrical ; 
the right exopod is three-segmented, the first segment bearing a stout, in- 
wardly directed, pointed projection ; the middle and proximal segments each 
bear a denticulated outer spine. The middle segment is prolonged beyond 
its spine, and its inner surface is concave with a small spine about mid-way 
along the margin and a cluster of spinules proximally, but no marked basal 
process. The smaller distal segment bears three spines, the middle being 
the largest and terminally denticulate and curved. The other two are 
smaller, the outer somewhat the larger and denticulate, the inner smooth 
and more slender. The right endopod is three-segmented. At outer distal 
corner of its middle segment is a short spine which curves inwards. Distal 
segment bears four ciliate setae. The left fifth leg is shorter than the right ; 
both exopod and endopod are peculiar in that they appear three-segmented 
if viewed from in front, but only two segments can be made out from behind. 
In the exopod it is the terminal segment which is incompletely divided. The 
basal segment bears a ciliate 'spine distally. The terminal segment has four, 
one of which is proximal to the incomplete dividing line. The terminal spine 
is the largest and is peculiarly bent. The inner distal corner is extended 
laterally into a rounded bulge with a postero-lateral groove or sinus. In 
the endopod it is the basal segment which is incompletely divided. There is 
a curved inner spine on the middle segment and three short spines, and an 
elongate outer spine that could almost be termed a seta on the distal 
segment. 
Discussion. 
Five species have been definitely assigned to this genus, and Nicholls 
(1944) suggests that Centropages pectinatus Brady described in 1899 from 
a damaged specimen is really referable to this genus, possibly referable 
to brevicornis , Henry, or subsalaria , Percival. In his paper Nicholls deals 
briefly with the probability that subsalaria is synonymous with brevicornis. 
The figures given by Percival are certainly very similar to those for brevi- 
cornis , particularly as shown by Dakin and Colefax (1940). The females of 
this genus are very similar and significant specific features are hard to find 
in the somewhat incomplete descriptions of the species. However, Kiefer 
for gracilis shows the coxal segment of the right fourth leg of the female 
with a straight short “feathered” seta. For subsalaria Percival records “a 
short feathered seta as in G. gracilis ” Dakin and Colefax figure it for 
brevicornis as a straight seta. Nicholls for inermis shows it curved distally 
and rather thickly ciliated. In ini pari pes it is distinctly curved and but 
sparsely ciliated. 
In spinosus the fifth endopod in the female is shorter than the exopod 
and does not reach beyond the centre of the middle exopod segment ; whereas 
in gracilis it reaches just to the end; in brevicornis it is figured as reaching 
half-way along the terminal exopod segment, and in subsalaria it is stated 
to reach one-sixth of the distance along. However, this may not be signifi- 
cant, only careful examination of material could tell. 
