90 ME. T. SCOTT ON ENTOMOSTEACA 



4tli (day collection). Station 22, 20 fathoms, February 4tli (day collection). Station 

 24, surface, February 6th (day collection). Lat. 7 ' 38' S., long. 12' 3' 3" E., surface, 

 February 9th (night collection). 



This Oilhona has long densely plumose setjB of a persistent purplish colour, which are 

 sufllciently conspicuous to enable the species to he readily distinguished. Oithona 

 plumifera, though frequent in the tow-nettings in which it was observed, appeared to be 

 somewhat rare generally, as the seven collections noticed above were the only ones in 

 which it was obtained. 



Oithona minuta, n. sp. (PL IX. figs. 14-25.) 



Length, female "64 mm., male -5 mm. Body moderately stout, ovate. Anterior 



antennee not reaching to the end of the thorax : in the female composed of nine distinct 



joints; the basal joint, which forms about a third part of the whole length of the 



antenna, is indistinctly divided into seven unequal portions by very faint lines that do 



not appear to be true joints. If these indistinct articulations be included the female 



antennfB will consist of fifteen joints, the proportional lengths of which are nearly as 



shown in the formula : — 



(32 . 4 . 4 . 13 . 4 . 4 . 4) . 14 ■ 24 . 34 ■ 10 ■ 16 . 6 . 12 . 11 

 (1 .2.3. 4 .5.0.7). 8 . . 10 . 11 . 12 . 13 . 14Tl5" 



The figures in parentheses refer to the indistinct pseudo-articulations observed in the 



elongate basal joint. Male antennae 11-jointcd, hinged between the ninth and tenth 



joints (fig. 16). Posterior antennse nearly as in Oithona spinlrostrls, Glaus (fig. 17) The 



principal branch of the mandible-palp is armed with two stout, curved, claw-like apical 



appendages bearing minute marginal spines ; the accessory branch is 4-jointed and 



furnished with several long plumose setoe (fig. 19). The biting part has on one side a 



short, stout, submarginal tooth, and on the other side a spiniform seta at the apical 



angle fully twice the length of the apical teeth (fig. 18). Anterior and posterior 



foot-jaws nearly as in Oithona Challengerli or Oithona sjmiirostris, as are also the 



swimming-feet. The feet of the fifth pair in the female are bisetose, with moderately 



long plumose setse ; those of the male very minute, with two very small setae. Abdomen 



of the female 4-, of the male 5-jointed ; stylets as long as the last abdominal segment ; 



the last abdominal segment and stylets in the male are a third shorter than in 



the female, the tail-seta? in the male arc also much shorter than in the female 



(figs. 24, 25). 



This minute but distinct Oithona was obtained in a tow-net gathering collected at 

 Bananah Creek, Congo River, February 7th ; the sp. gr. of the water was only 1-00870. 

 In two tow-net gatherings from the seaward portion of Loanda Harbour, February 15th, 

 surface-temperature of the water at noon 79"-2 F. : the Loanda Harbour tow-net 

 gatherings were collected during the afternoon. Oithona minuta was moderately common 

 in these last two gatherings, and many of the females carried ovisacs. 



