2 43 
and somewhat narrowed in front, the hinder segments not expanded 
laterally; urosome slender (fig. 33), the genital segment not dilated 
and scarcely longer than the next following segment, the first two 
segments armed with spine-like setae on their distal outer angles, 
last segment having its distal margin finely aculeate ; caudal rami rather 
longer than the last abdominal segment; setae of the outer margin 
attached near the middle; apical setae of moderate length. Anterior 
antennae (fig. 34) eight-jointed, barely half as long as the first 
segment of the body, sparingly beset with short setae. Natatory 
feet short, having both rami two-jointed (fig. 34); the place of the 
fifth pair occupied by two short setae. 
This species occurred in the same localities as those recorded for 
C. nigeriae. It is the smallest which has ever come under my notice. 
The characters of the urosome and anterior antennae sufficiently 
distinguish it from any other form. 
Diaptomus nigerianus, n. sp. Plate XIX, figs. 24-30. 
Female, length i'i mm. Anterior division of the body rather 
slender, of nearly equal width throughout, the posterior segment some¬ 
what produced laterally and sharply angulated (fig. 28); urosome 
(fig. 25) slender, the genital segment not at all protuberant in front, 
the last two segments together scarcely half as long as the genital 
segment, and very imperfectly separated from each other; caudal 
rami dilated distally, scarcely as long as the two anterior coalescent 
segments, terminal setae broad, sub-spathulate and rather densely 
plumose, about twice as long as the rami themselves (fig. 25). 
Anterior antennae slender, scarcely exceeding the entire length of 
the body; posterior maxillipeds of the usual form, the distal joint 
exceedingly small (fig. 26); inner ramus of the last pair of legs 
fig- 27) simple, much shorter than the first joint of the outer ramus; 
claw of the outer ramus stout, non-ciHated, terminal joint indistinct. 
Male, last segment of the cephalothorax rounded off posteriorly; 
abdomen narrow, five-jointed ; penultimate joint of the right anterior 
antenna bearing an apical spine, which is shorter than the next 
following joint (fig. 24); outer branch of the last pair of legs 
fig- 3 °) of the right side simple, the last joint bearing an apical 
sirnply_ curve d claw, and on the outer margin a small papilla and 
a slender curved spine; the basal joint of the foot of the left side is 
