1903. ] IN THE ‘ CHALLENGER’ COLLECTION. 61 
shape and with the marginal spine well developed.—Length 
o4 mm. 
The species is easily distinguished from S. arcticus Kr. by the 
shape of the rostrum, together with the anterior margin of the 
scutum, and especially by the branchiz above trl.* and trl.’; in 
all other features these two species are closely allied. 
SERG. CHALLENGERI, n, sp. (Plate XII. figs. 2 a—2 n.) 
The type of this species is the specimen on which Bate writes 
(p. 390): “Station 173, July 24th, 1874; lat. 19° 9' 35” S., 
long. 179° 41’ 50” E.; off Matuku, Fiji Islands; depth 315 
fathoms; bottom, coral mud. One specimen, male. Dredged. 
Length 24 mm.” He referred it to S. atlanticus. I have the 
pleasure of appending the name of the renowned ship to this 
Sergestes, which is one of the most interesting species of Crustacea 
secured by the expedition. Unfortunately the single specimen is 
very mutilated. 
The rostrum (fig. 26) is rather low, short, obliquely triangular, 
turning somewhat upwards; its apex is acute and very slightly 
produced. The supra-ocular spine is wanting; the hepatic spine 
is rudimentary; the gastro-hepatic groove (fig. 2 a) is deep, and 
the cervical groove very distinct. The eyes have been broken off, 
only the basal part of the stalks being left. In the antenn. ped. 
(fig. 2c) the outer margin of the basal joint is a little longer than 
that of the two other joints together; the second joint is 
moderately robust, its inner margin a little more than three 
times longer than the breadth; the third is slightly more than 
two and a half times longer than broad, a little shorter than the 
outer margin of the second joint, and only three-fifths as long as 
the inner margin of the last-named joint. The squama of the 
antenna is distally very broad (fig. 2c), with the outer spine 
scarcely projecting beyond the terminal margin. Mxp.’ and trl.*— 
trl.’ are wanting; of trl.’ the apical part has been lost, but these 
legs seem to have been a little longer than mxp.*, and to be more 
slender than in S. arcticus, but otherwise not showing any 
difference of importance. Of the branchie (fig. 2d), br. above 
trl and trl.’ are long and narrow; br.’ above tri.? is as usual a 
lamella; br." above tril.’ is slightly more than one-third as long 
as br., especially with its anterior branches well developed; of the 
branchie above trl.*, br. is about three-fourths as long as br. above 
trl.’, while br." is proportionately large, much longer and broader 
than br.' above trl.*, and even more than half as long as br. above 
trl” The ext. br. of urp. (fig. 22) has the apical portion 
wanting, but the branch seems to have been nearly five times 
longer than broad, with the marginal spine well developed and 
situated as in S. arcticus.—Length 23 mm. 
By the shape of the joints of the antenn. ped., the development 
of the branchie above trl.* and trl.*, and the shape of the ext. br. 
of urp., this species is related to S. robustus Smith, 8. prehensilis 
Bate, and S. kréyert Bate. But it is sharply distinguished from 
