COPErODA FROM CHRISTMAS ISLAND. 18Q 



. 2nd maxilla and maxillipede (PI, XXX. fig. 8) of the usiial 

 form but rather short. 



1st foot (PI. XXXI. fig. 7) : exopodite with 1.1. 3 outer edge 

 spines and 1.1.4 inner edge sette, the inner edge seta on the 

 1st joint being very small; terminal spine shorter than the 

 exopodite ; endopodite with 1.1.4 inner edge and 0.0.1 outer 

 edge seta?; there is a distinct tooth between the terminal and 

 the outer edge seta ; inner edge seta on the 2nd basal longer 

 than the first two joints of the endopodite. 



2nd and 3rd feet (PI. XXXI. figs. 8, 9) with 1.1.3 outer 

 edge spines and 1.1.5 inner edge set^e, the inner edge seta on 

 the 1st joint being very small ; terminal spine of 2nd foot a little 

 longer than the exopodite and of 3rd foot about equal to it ; in 

 both cases it is considerably longer than the endopodite ; inner 

 edge seta on 1st basal of 3rd foot and outei- edge seta on 

 2nd basal, both these setfe being absent from the 2nd foot. 



4th foot (PL XXX. fig. 9) : exopodite with 1,1.2 outer edge 

 spines and 1.1.5 inner edge setse, the inner edge seta on the 

 1st joint being very small, tei^minal spine slightly longer than 

 the exopodite ; endopodite with 1.2.3 inner edge and 0.0.1 

 outer edge setae ; 1st basal with inner edge seta, 2nd basal with 

 outer edge seta. 



5th foot small, with two terminal setfe and one at its base. 



This species is closely allied to 0. i^igida, differing mainly from 

 it in the greater length of the terminal spines of the swimming- 

 feet. In 0. 7-igida, as figured by Giesbrecht (14) and also by 

 Cleve (7), these spines are shorter than the terminal joints of 

 the exopodites. Another diff'erence is the comparatively large 

 size of the inner edge setee on the 1st joints of the exopodites in 

 0. rigida. In 0. oculala they are very small. In size and appear- 

 ance and in the proportional lengths of the abdominal segments 

 and antennal joints the two species agree very closely. 



Common in one gathering, a single specimen in another. 



Genus Paroithona. 



This genus was described in 1908 (10) from specimens taken 

 in deep water ofli" the west coast of Ireland, only one species 

 having been met with until the Christmas Island collections 

 yielded a second representative. The genus is closely allied to 

 Oithona, iimd is distinguished mainly by having a two-jointed 

 endopodite on all the swiiTiming-feet and by the form of the 

 mandible palp. It is questionable whether the difTerences which 

 separate it from some species of the genns Oithor.a are ai y 

 greater than those which separate 0. nana from such species as 

 0. plumifera and 0. setigera, but the occurrence of a second 

 species, closely resembling that first described, is in favour of thie 

 retention of the e'enus. 



