1896. ] OF THE GENUS SERGESTES. 957 
the Atlantic (incl. the Mediterranean and the Arctic sea at 
Greenland). This is of importance for the reference of larval stages, 
as Bate has established the species :—S. dorsospinalis, Bate (p. 394, 
pl. lxxii. fig. 1) and S. laterodentatus, Bate (p. 395), captured 
“associated with” another ‘South of Australia”; S. nasidentatus, 
Bate (p. 398, pl. xxii. fig. 2), ‘between Valparaiso and Juan 
Fernandez”; SS. rinkii, Bate, vix Kroyer (p. 404, pl. Ixxiil. fig. 3), 
“ New Hebrides ” and “ South Pacific”; and S. leviventralis, Bate 
(p. 425, pl. xvii. fig. 3), “ North of New Guinea”—which 5 reputed 
species are all larvee and all belong to two or three species closely 
related to S. arcticus, Kr., or perhaps partially belong to that 
species. But Bate’s representations are not sufficiently good for 
the decision of such questions: thus, f. inst., the chances are that he 
has overlooked the hepatic spine in some of the “ species,” while 
S. laterodentatus, Bate, has obviously been established on a specimen 
with a long hepatic spine, which has given rise to the name. His 
description of S. rinkit either involves the fault that the rostrum, 
which is described and figured as short, has been broken off, or the 
form must decidedly be different from S. rinkii, Kr., as a short 
rostrum and dorsal abdominal spines are not coexistent in this 
latter species.—In all probability Bate’s 5 species belong to two or 
three of the other known species of the arcticus-group, and none 
of them to S. arcticus, Ky., itself. 
Further elucidation of the adults and the larve of the arcticus- 
group I am not able to derive from existing literature. Yet the 
result has been.that 2 adult and 2 larval species have been cancelled 
as belonging to S. arcticus, Kr., and the other related forms ; 3 adult 
species and 4—5 Jarve have been collocated into the group ; finally 
one new species has been established. 
B. S. corniculum, Kr.—The stage described and figured by 
Kroyer (p. 252, tab. ii. fig. 4, ae) and Bate (p. 410, pl. Ixxv. 
fig. 1) is a half-grown larva. The mature formis unknown. The 
adult with black eyes, 20-22 mm. long, is rather remarkable, as 
the body is extraordinarily slender, with a considerable distance 
between the mouth and the eyes, thus in that respect approaching 
to S. tenwiremis, Kr., and being intermediate between this species 
and f. inst. S. arcticus, Kr. Its rostrum is a little lower than in 
S. arcticus, Kr., the supraocular spine rudimentary or lacking, the 
hepatic spine short, the gastro-hepatic groove distinct. The eyes 
are but a little broader than the end of the stalk; in the long 
antenn. ped. the first joint is considerably longer than the third 
and this considerably longer than the second. An interesting 
character is that the sixth joint of mxp.’ is divided into 4 sub-joints, 
the distal three of equal length and the first somewhat longer, 
and each of these 4 joints is more or less distinctly divided into 
2 joints: thus we obtain 8 sub-joints, of which 7 possess a long seta 
or slender spine on each side near the apex, but the two spines are 
not placed opposite to each other, and the last sub-joint has a pair 
of slender apical spines. The branchiz recall those in S. azcticus, 
Kr.: above tri’ two branchie, the first long, the second several 
