1909. ] OF THE THIRD TANGANYIKA EXPEDITION. 63. 
34, CYCLOPS DUBIUS, sp.n. (Plate XXI. figs. 205-207.) 
Specific Characters.—FrmMaue. Body (fig. 205) rather slender, 
with the anterior division oblong-oval in form and obtusely 
rounded in front. Last pedigerous segment (see fig. 206) with 
the lateral parts rounded off and clothed with unusually long and 
delicate hairs. Urosome considerably exceeding half the length 
of the anterior division and somewhat tapering behind; genital 
segment only slightly widened in front. Caudal rami (fig. 207) 
long and slender, sublinear m form and slightly divergent, con- 
siderably exceeding in length the last two segments combined, 
outer edge perfectly smooth with a small seta near the end; 
innermost apical seta small, being much shorter than the outer- 
most, which is spiniform; middle sete of moderate length and 
uniformly ciliated, the inner one about twice as long as the outer ; 
dorsal seta not much produced. Anterior antenne rather short, 
not nearly attaining the length of the cephalic segment and 
composed of 12 articulations. Last pair of legs (see fig. 206) 
each consisting of a single somewhat lamellar joint extended 
laterally, and provided with three comparatively short spiniform 
sete. 
Length of adult female 0°62 mm. 
Remarks.—The exact relation of this form to the other known 
species is as yet somewhat doubtful, as the solitary specimen 
examined has not been dissected. Yet, in spite of the perfectly 
smooth outer edge of the caudal rami, the short anterior antenne, 
and the laterally extended last pair of legs, it may probably belong 
to the group for which C. serrulatus is the type. In any case 
it may be regarded as a rather abnormal form. 
Occurrence.—The above-described specimen was found in a 
sample from Nyasa, taken 15/6/04 in the Anchorage Bay, south 
end of the lake. 
Sect. Peecilostomata. 
Fam. ERGASILIDG4. 
This family comprises a peculiar group of peecilostomatous 
Cyclopoida, which in some respects forms as it were a transition 
to the true parasites, Caligoida and Lerneoida. The adult 
females, which in some cases appear rather much deformed, are 
found firmly attached. by the aid of their clawed posterior 
antenne, to the gills of several species of freshwater fishes. The 
copulation of the sexes in all probability takes place before 
the fixation of the female, in the last free stage of the latter. 
We know of two distinct genera of this family, viz. Argasilus 
Nordman and 7hersites Pagenstecher. To these a third genus is 
here added. 
Genus ERGASILOIDES, n. g. 
Generic Characters.—Body of female (in last free stage) cyclo- 
poid in shape, subdepressed in front, and attenuated behind; in 
