322 DR THOMAS SCOTT ON THE 



with a tolerably stout, short, but prominent tooth on the lower aspect, while the third 

 joint carries a moderately long sensory filament. Antennae small ; outer ramus uni- 

 articulate. Mandibles small and provided with a small one-branched palp. 



Thoracic legs small. In tlie first pair, the inner ramus is rather longer than the 

 outer, and the proximal joint is nearly twice as long as the end one. In the next three 

 pairs, the inner ramus is very sliort, and the proximal joint extremely small (see 

 figs. 16-19). 



The fifth pair has the basal joint tolerably broad and lamelliform, and produced 

 interiorly to near the end of the second joint ; the distal half of the inner margin of the 

 basal joint is obliquely and somewhat unevenly rounded, and furnished with five setse, 

 three on the inner margin and two at the apex ; the second joint is moderately 

 narrow, its width at the widest part being scarcely equal to half the length : this 

 joint bears six setae ; the apical seta is tolerably stout and elongated, but the one on 

 either side of it is small ; the other three setie, which are of moderate length, spring 

 from the outer margin, as shown in the drawing (fig. 20). 



Male. — In the male, the antennules are modified to form grasping organs. The 

 inner ramus of the second pair of thoracic legs is three-jointed, and the second joint is 

 produced into a long and tolerably stout spiniform appendage (fig. 21). In the fifth pair, 

 which are very small, the basal joint is scarcely produced interiorly, and is provided 

 with two short setse ; the outer joint is short and narrow, and furnished with three 

 small setse on the outer margin and two at the apex (fig. 22). 



Habitat. — Scotia Bay, South Orkneys, in siftings from some dredged material 

 collected in June 1903 ; Station 325, 60° 43' 42" S., 44° 38' 33" W. 



Remarks. — This species, though not very common, has apparently an extensive 

 distribution. Professor G. 0. Sars records it from Skjserstad Fjord in Norway — ^just 

 within the Arctic Circle, and Dr G. S. Brady from a few British localities. Dr Glaus 

 obtained the species in the Mediterranean, and it also occurred in collections from the 

 Gulf of Guinea brought home by the telegraph steamer Buccaneer. After a careful 

 examination of the South Orkney specimens, I am unable to discover any essential 

 diff'erence between them and those described by the authors mentioned above. 



Tribe CYCLOPOIDA. 



Fam. OiTHONiD^. 



Genus Oithona, Baird, 1843. 



Oithona plumifera, Baird. 



1843, OUhona plumifera, Baird, "Notes on British Entomostraca," Zoologid, vol. i. pp. 193-197. 



This species was observed in gatherings from various stations, extending from 



Station 11, 23° 50' N., 21° 34' W., in the North, to Station 68 in the South Atlantic, 



Pernambuco, 7° 42' S., 34° 32' W. Its distribution, which is widely extended, reaches 



to at least as far north as the British Islands. 



(ROY. SOC. EDIN. TRANS., VOL. XLVIII., 568.) 



