184 MR. G. P, FARRAN ON 



There are two imperfect jointings close together in the centre of 

 the third joint and another in the sixth ; a row of minute 

 spinules runs along the lower edge of the fovirth and fifth joints. 

 2nd antenna large, robust, of the usual form. 

 Mandible (fig, 2) with very slender 2nd basal ; endopodite with 

 four small setae, the two central ones being the shortest ; exopodite 

 with four large feathered setse and one slender one. 



1st maxilla (fig. 3). — 1st inner lobe well developed with the 

 usual setse ; 2nd inner lobe with one fine seta ; 3rd inner lobe 

 with three spines ; endopodite comparatively large with three 

 very small setee ; exopodite with four setse. 



2nd maxilla and maxillipede of the xisual structure but com- 

 paratively short. 



1st foot (fig. 6) : exopodite with 1.1.3 outer edge spines and 

 1.1.4 inner edge setse, the seta on the inner edge of the 1st joint 

 being very minute, terminal spine long and slender, longer than 

 the exopodite ; endopodite with 0.1.4 inner edge and 0.0.1 

 outer edge setse. 



2nd foot (fig. 7) : exopodite with 1.1.3 outer edge spines and 

 1.1.4 inner edge setse, seta on inner edge of 1st joint very 

 minute, terminal spine longer than the exopodite and broader 

 than in the 1st foot; endopodite with 1.2.4 inner edge and 

 0.0.1 outer edge setse. 



3rd foot (fig. 8) : exopodite with 1.1.2 outer edge spines, the 

 most distal very large, the rest very minute, and 1.1.4 inner 

 edge setse, terminal spine much longer than the exopodite ; 

 endopodite with 1.2.4 inner edge and 0.0.1 outer edge setfe. 



4th foot rather small : exopodite appears to have 1.1.3 or 

 1.0.3 very minute slender outer edge spines and 1.1.4 inner 

 edge setse ; endopodite with 1.2.3 outer edge and 0.0.1 inner 

 edge setse. 



5th foot of usual form. 



The possession of a pointed rostrum and of a large number of 

 outer edge spines, though reduced in size, on the swimming-feet, 

 and also the presence of a large endopodite on the 1st maxilla, 

 places this species near to 0. rohtLsta, but the 1st antenna is of a 

 diflferent type and seems to be peculiar in not having a spine on 

 the distal end of the 3rd (primitively 12th) joint. As 0. rohusta 

 is the least specialised of the rostrate Oithonas, so 0. vivida seems 

 to have taken the first step towards the reduction of the spines 

 on the swimming-feet which is found in the other rostrate 

 species. 



Four specimens were found in one gathering. 



OiTHONA ROBUSTA Giesbrecht. 



Found in four gatherings, a few specimens in each. 

 Distribution. Indian Ocean and Tropical Pacific. 



OlTHONA DECIPIENS, Sp. n. (PI. XXYIII. figS. 4-11.) 



Female (fig. 7). — Length •56-'62 mm. ; cephalothorax '34 mm. ; 



