64 PROF. G, 0. SARS ON THE COPEPODA [Jan. 12, 
male of more slender form. Head distinctly defined from meta- 
some and very large, more or less scutiform and without any 
rostrum, Segments of metasome rapidly diminishing in size, the 
fifth or last very small, almost obsolete. Uvrosome short, and 
consisting in female of only two, in male of three segments ; 
genital segment in both sexes large and tumid, that of male 
having the postero-lateral corners produced and tipped with a 
small spine. Caudal rami short, each carrying on the inner 
corner a strong seta, which in some cases is bifid, outer corner 
provided with three much smaller sete, one of which is extended 
outwards. Anterior antenne of a similar structure in the two 
sexes, comparatively short and stout, 5- or 6-articulate, and 
densely clothed with delicate sete. Posterior antenne transformed 
into strong prehensile organs, larger in female than in male. 
Oral area produced in the form of a short tube issuing from the 
ventral face of the head behind, and provided inside with two 
pairs of incurved appendages (mandibles and maxille), outside 
with a small lamella (maxilliped), which in male is transformed 
into a well-developed prehensile organ terminating in a clawed 
hand. Natatory legs with the rami more or less meurved and 
clothed at the end with slender ciliated seta : those of the fourth 
pair much smaller than the others, with the number of joints in 
the outer ramus reduced. Last pair of legs extremely small and 
rudimentary, knob-like, with a single small seta on the tip. 
Adult stage of female still unknown. 
Remarks.—Vhis new genus is chiefly distinguished from H7rga- 
silus, to which it bears a close resemblance, by the reduced 
number of segments in the urosome of both sexes. In the corre- 
sponding stage of Hrgasilus the urosome is composed in the 
female of four well-defined segments and in the male of five such 
segments. Moreover, the very rudimentary condition of the last 
pair of legs and of the segment to which they ave attached, is 
yather characteristic. Three different species of this genus have 
been determined. 
35, ERGASILOIDES MEGACHEIR, sp.n. (Plate XXII. figs. 208— 
Specitic Characters.—FEMALE in last free stage. Body (figs. 208 & 
209) comparatively short and stout, pronouncedly depressed, and, 
viewed dorsally, subpyriform in outline. Head very large and 
expanded, almost quadrangular in form ; dorsal face with a well- 
marked transverse fold at about the posterior third of its length, 
and moreover exhibiting two small but sharply defined areas, the 
one of circular form and occurring in front of the middle, the 
other cordiform and placed near the posterior edge; frontal edge 
of the head transversely truncated, postero-lateral corners only 
slightly prominent and rounded. The four anterior segments of 
metasome with the lateral parts slightly produced backwards but 
obtusely rounded at the end. Last segment almost wholly 
concealed. Urosome scarcely exceeding in length one-third of 
