34 PROF. G. 0. SARS ON THE COPEPODA [Jan. 12, 
in D. galebi, though, on a closer comparison, differmg in some 
particulars. Right leg with the 2nd basal joint produced at the 
end, on the posterior face, to a short, somewhat faleiform incurved 
lamella, inner edge perfectly smooth; proximal joint of outer 
ramus terminating outside in an obtuse corner; distal joint 
pyriform in shape, with a very delicate scale-like projection on 
the posterior face, about in the middle between the apical claw 
and the lateral spine, the latter attached much nearer to the base 
than to the end of the joint ; apical claw much curved and finely 
denticulated inside for some part of its length. Left leg with 
the outer ramus distinctly biarticulate and terminating in a well 
defined digit accompanied by a small ciliated bristle; imner edge 
divided into two rounded and finely ciliated lobules. 
Length of adult female 1-30 mm. 
Remarks.—Vhis form has been identified by Dr. Mrazek with 
the Egyptian species, J). galebi Barrois, apparently owing to a 
certain similarity in the structure of the last pair of legs in the 
two sexes. I find, however, that the present form differs in so 
many other points from the above-named species, as more fully 
described by Dr. Richard *, that I have felt justified in regarding 
it as specifically distinct, though nearly related to D. galebi. The 
specific name here proposed alludes to this near relationship of 
the two species. 
Occurrence.—This form occurred in great abundance in a 
sample taken 25/4/05 off the island Bukoba, western shore of 
Victoria Nyanza. The same species has also been recorded pre- 
viously by Dr. Mrazek and Dr. von Daday from other localities, 
and seems indeed to be one of the most characteristic plankton- 
forms of that lake. Together with the usual form, there also 
occurred in the same sample a much smaller variety of somewhat 
more slender body and with the anterior antenne more elongated, 
but otherwise agreeing in all structural details exactly with the 
larger form. 
2. DIAPTOMUS MIXTUS, sp.n. (Plate VII. figs. 9-17.) 
Specific Characters.—FrmMaue. Body (figs. 9 & 10) comparatively 
more slender than in the preceding species, with the anterior 
division narrow oblong in form and having its greatest width 
about in the middle. Last segment of metasome, as in D. gale- 
boides, confluent with the preceding one, but having the lateral 
corners distinctly projecting, each armed with two well-defined, 
sharply-pointed mucros (see fig. 11), the one issuing somewhat 
more dorsally. Urosome conspicuously asymmetrical, its terminal 
part being more or less turned to left side; genital segment 
(fig. 11) gradually widening in front, and armed on each side 
with a small, though distinct mucro; last two segments con- 
fluent, and combined not attaining half the length of the genital 
segment. Caudal sete normal. Anterior antenne very slender 
* Revue biologique du nord de la France, tome y. 1892-93. 
