1896.] OF TUB GENUS SBBGBSTES. 957 



the Atlantic (incl. the Mediterranean and the Arctic sea at 

 Q-reenland). This is of importance for the reference of larval stages, 

 as Bate has established the species : — S. dorsospinalis, Bate (p. 394, 

 pi. Ixxii. fig. 1) and S. laterodentatus, Bate (p. 395), captured 

 " associated with " another " South of Australia" ; ;5?. nasidentatus. 

 Bate (p. 398, pl. Ixxii. fig. 2), " between Valparaiso and Juan 

 Fernandez "; S. rinJcii, Bate, vix Krbyer (p. 404, pl. Ixxiii. fig. 3), 

 " New Hebrides " and " South Pacific " ; and S. Iceviventi-alis, Bate 

 (p. 425, pl. Ixvii. fig. 3), " North of New Guinea" — which 5 reputed 

 species are all larva> 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 sufllciently good for 

 the decision of such questions : thus, f . inst., the chances are that ho 

 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. rhikii either involves the fault that the rostrum, 

 which is described and figured as short, has been brolten off, or the 

 form must decidedly be different from 8. rinJdi, Kr., as a short 

 rostrum and dorsal abdominal S])ines 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 arclieus-gion]), and none 

 of them to S. arcticus, Kr., itself. 



Further elucidation of the adults and the larvae of the arcticus- 

 group I am not able to derive from existing literature. Tet 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 larva; 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. iii. fig. 4, a-e) and Bate (p. 410, pl. Ixxv. 

 fig. 1) is a half-grown larva. The mature form is 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. tenuiremis, 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 branchias recall those in S. arcticus, 

 Kr. : above trl.^ two braiichia;, the first long, the second several 



