1909. | OF THE THIRD TANGANYIKA EXPEDITION. 51 
by the comparatively shorter innermost caudal seta. In C. oithon- 
oides this seta is about the same length as the outer mediate one, 
whereas in the present species it is scarcely more than two-thirds 
as long. The extraordinary length of the dorsal seta has also 
been noted by Dr. Mrazek. He has, however, not been aware of 
the rather striking difference from most other species in the 
structure of the posterior antennz. According to its organisation, 
this species, ike C. lewckarti, may be regarded as a true limnetic 
or planktonic form. 
Occurrence.—I have only found this form in one of the samples, 
viz., that from Bukoba, Victoria Nyanza. It did not occur in 
any ‘abundance, Dr. Mrizek has recor ded it also from the island 
Djuma in the same lake. 
17. CYCLOPS NEGLECTUS, nom. nov. (Plate XIV. figs. 113- 
Ute) 
Syn.: Cyclops hyalinus Richard (not Rehberg). 
- oithonoides Mrazek (not G. O. Sars). 
Specific Characters.—Frmaun. Body (fig. 113) much shorter 
and stouter than in the preceding species, with the anterior 
division regularly oval in form and the front evenly rounded. 
Last pedigerous segment small, not produced later ally. Urosome 
about half the length of the anterior division, and having the 
genital segment slightly widening in front. Caudal rami (fig. 117) 
very short, searcely exceeding in length the anal segment, and 
almost twice as long as they are broad ; seta of outer edge attached 
at about the posterior third of the ramus; apical setae compara- 
tively short, immermost one not attaining half the length of the 
outer mediate seta and scarcely twice as long as the outermost ; 
dorsal seta of moderate length. Anterior antenne not nearly 
attaining the length of the anterior division of the body, and 
17-articulate. Posterior antennze (fig. 114) of normal appearance, 
with about nine anteriorly-curving setze on the penultimate joint 
Natatory legs with the rami less Slender than in C. emini; inner 
ramus of fourth pair (fig. 115) with the apical spines very unequal 
in size. Last pair of legs (fig. 116) resembling those in the said - 
species, though having the lateral spine of the distal joint com- 
paratively shor ter. Ovisacs not very lar ge, oval in form, and only 
containing a limited number of ova. 
Length of adult female 0°73 mm. 
Remarks.—This form is closely allied to the European species 
CO. hyalinws Rehberg, and indeed Dr. Richard, and formerly 
also I myself, identified it with that species. It is, however, on 
a closer comparison, at once distinguished by the much shorter 
innermost caudal seta. Whereas in Oh yalinus this seta is about 
the same length as the outer mediate one, it is in the present form 
searcely more than half as long. Dr. Mrazek has identified this 
form with C. oithonoides G. 0. Sars, to which species it in reality 
bears only a very remote resemblance. 
Ae 
