1. Oithona spinirostris, Glaus. 

 (PI. i & ii). 



Oithona spinirostris, Glaus, Die freilebenden Copepoden, p. 105, PI. XI, figs. 4 9. 



Syn: Oithona challengeri, Thompson. 



plumifera, Scott, (not Baird). 

 atlantica, Fai-ran. 



Specific Characters. Female. Body exceedingly slender, with the anterior 

 division narrow fusiform in shape, the greatest width scarcely exceeding Vs of 

 the length and occurring somewhat in front of the middle. No conspicuous plumes 

 present laterally. Rostrum strong, spiniform, and only very slightly curved, so 

 as to be visible in the dorsal aspect of the animal. Tail not much shorter than 

 the anterior division and very narrow ; genital segment about the length of the 2 

 succeeding segments combined, and conspicuously dilated in its anterior part. 

 Caudal rami nearly as long as the anal segment and rather divergent, seta of 

 outer edge attached close to the base, the 2 middle apical setse almost twice the 

 length of the tail. Eye narrow linear in form and of a deep red colour. Anterior 

 antennae very slender and elongated, reaching, when reflexed, to the end of the 

 2nd caudal segment, and composed of about 12 more or less distinctly defined 

 joints of rather unequal length and carrying scattered exceedingly long setse 

 pointing in different directions. 1st pair of natatory legs with the inner ramus 

 distinctly 3-articulate, all joints of outer ramus spiniferous outside. 2nd and 3rd 

 pair with no spine outside the middle joint of the outer ramus, terminal joint of 

 this ramus, as in the 1st pair, with 2 spines outside. 4th pair with no spines 

 outside the first 2 joints of the outer ramus and with only a single setiform spine 

 outside the terminal joint. Ovisacs narrow oblong in form and greatly divergent, 

 in some cases extending nearly at right angles to the axis of the body, each 

 sac containing only a limited number of very pellucid ova, generally arranged 

 in a double row. 



Male much smaller than female and of a rather different appearance, 

 the body being comparatively less slender, with the front obtusely truncate and 

 wanting any trace of a rostrum. Tail distinctly 5-articulate, with the 1st or 

 genital segment greatly swollen, to receive the 2 spermatophores. Caudal rami 

 shorter than the anal segment and not at all divergent, apical setse much shorter 

 than in female and of quite normal appearance. Anterior antennse scarcely 

 longer than the anterior division of the body and exhibiting the usual geniculation ; 

 middle section only slightly tumefied, terminal one biarticulate. Natatory legs 

 with all the joints of the outer ramus spiniferous outside, 3 such spines being 



