2 17 



The abdomen is composed of four segments. The genital segment is large. It is much 

 contracted in the distal half, which is separated from the anterior portion by a distinct suture 

 traversing the dorsal surface of the segment. The second, third and fourth segments are com- 

 paratively short. The fnrcal joints are one and a half times longer than broad (Plate LXIII, 

 fig. 24). 



The antennules are moderately long and slender and are eight-jointed. The last four 

 joints are narrower and shorter than the first four joints (Plate LXIII, fig. 16). 



The exopoclite of the antennae is rather long and slender, and one-jointed. It is furnished 

 with one strong apical seta and one slender marginal seta (Plate LXIII, fig. 1 7). 



The mandibles, maxillae and maxillipedes are nearly similar to those of Dactylopodclla 

 flava (Claus). 



The exopodite of the first pair of feet is three-jointed. The endopodite is two-jointed. 

 The first joint of the endopodite is moderately wide and is nearly as long as the combined 

 length of the joints of the exopodite. The second joint is short. The apex is furnished with a 

 long slender, slightly curved claw, and tvvo setae (Plate LXIII, fig. 22). 



The second, third and fourth pairs of feet are nearly similar to those of Dactylopodclla. 



The fifth pair of feet is somewhat foliaceous. The inner expansion of the proximal joint 

 is furnished with three strong inner marginal spines, and two apical spines. The distal joint is 

 short and wide. It is furnished with six setae at the distal end (Plate LXIII, fig. 23). 



Male unknown. 



Occurrence. — One specimen was found in the surface plankton collected at Station 

 40, off Pulu Kawassang, Paternoster Islands. 



Genus Pseudothalestris Brady, 1883. 



This genus was established by Professor G. S. Brady in 1883, in the report on 



the 'Challenger' Copepoda. It is closely related to the genus Westwoodia Dana, in the 



structure of the appendages, but it differs very considerably in having the exopodite of the 



first pair of feet composed of two distinct joints. The exopodite is only one-jointed in true 



Weshvoodia . 



Professor G. O. Sars 'Crustacea of Norway' Vol. V, disestablished this genus, owing 

 to the fact that he obtained a species ( Weshvoodia assimilis) with the exopodite of the 

 first pair of feet composed of two joints, but in all other respects agreeing so closely with 

 the type of the genus Westwoodia that a very careful examination was required to separate 

 it from Weshvoodia nobilis (Baird). This reason appears to be scarcely sufficiënt for cancelling 

 Pseudothalestris especially as it is a common occurrence to find species belonging to different 

 genera included under one family that possess some character common to all, yet differing 

 in other points. The two-jointed exopodite of the first pair of feet is evidently not accidental, 

 and it is surely of as much value in generic distinction as the large fifth pair of feet of 

 Phxllothalestris, or the greatly developed rostrum of Rhynchothalcstris, which are regarded 

 by Sars of so much importance, that he separates these forms from typical Thalestris. 



217 



S1BOOA-EXPED1TIE XXIXfl. 2 ^ 



