1909. | OF THE THIRD TANGANYIKA EXPEDITION. 65 
the metasome; genital segment much dilated, rounded oval in 
form. Caudal rami about the length of the last segment, with 
the seta of the inner corner simple and pointing straight behind. 
Anterior antennee (fig. 210) consisting of six well-defined articu- 
lations gradually diminishing in size. Posterior antenne (fig. 211) 
very largely developed ; propodus twice as long as the basal joint 
and oblong in form, being scarcely narrowed distally, anterior 
edge with a thin hyaline border not fully extending to the base ; 
dactylus about half the length of the propodus and somewhat 
twisted, its terminal claw comparatively short, with a recurved 
denticle inside. Oral parts (see figs. 212-215) exhibiting the 
structure characteristic of the genus. Natatory legs (figs. 216— 
218) with both rami distinctly 3-articulate, except the outer 
ramus of 4th pair (fig. 218), which is only biarticulate. Last 
pair of legs (fig. 219) extremely small. 
MALE (fig. 220) smaller than female and of considerably more 
slender form. Head much less expanded and rounded in front, 
its dorsal face without any distinct sculpturing. Segments of 
metasome evenly rounded laterally. Urosome more slender than 
in female and about half the length of the metasome. Anterior 
antenne only 5-articulate. Posterior antenne (fig. 221) much 
smaller than in female and of simpler structure. Maxillipeds 
(fig. 222) well developed, with the dactylus very slender. 
Length of female in last free stage 0°62 mm., of male 
0°55 mm. 
Remarks.—This form is especially distinguished by the great 
size and peculiar structure of the prehensile posterior antenne in 
the female, which character has given rise to the specific name 
here proposed. 
Occurrence.—Three female specimens (in the last free stage) 
and some few immature ones were found in a sample from 
Tanganyika, taken 13/10/04 at Sumbu, south-western shore of 
the lake. 
36. ERGASILOIDES MACRODACTYLUS, sp. n. (Plate XXIII. 
figs. 223, 224.) 
Specific Characters. —F EMAL (in last free stage). Body (fig. 223) 
resembling in its general shape that of the preceding species, 
though perhaps a little more slender. Head very large and 
expanded, subquadrate in outline, with the dorsal face sculptured 
in a similar manner to that in the preceding species, frontal 
margin transversely truncated, postero-lateral corners distinctly 
projecting, subangular. Urosome with the genital segment less 
tumid, inner caudal seta simple. Anterior antenne composed 
of only five articulations. Posterior antenne (fig. 224) very 
long and slender ; propodus fully twice as long as the basal joint 
and attenuated distally, with no hyaline border; dactylus re- 
markably elongated, almost attaining the length of the propodus, 
with the terminal claw slender and perfectly smooth. Legs of 
apparently the same structure as in the preceding species. 
Proc. Zoou. Soc.—1909, No. V. 5 
