I. '08. 30 



Sergestes arcticus, Kroyei. 



Plate III, figs. 13-19. 



Sergestes articus, Kroyer, 1859, PI. 3, figs. 7 a-g ; PI. 5, 



fig. 16. 

 Sergestes Meyeri, Metzger, 1875, PL 6, fig. 7. 

 Sergestes arcticus, Smith, 1882, PI. xvi, fig. 4. 

 Sergestes arcticus, Smith, 1886, PL xx, figs. 1 and 2. 

 Sergestes magnificus , Chim, 1888, PL 4, figs. 4 and 5. 

 Sergestes arcticus, Hansen, 1896. 



Sergestes articus, Hansen, 1903 (1), PL xii, fig. 1, a-c. 

 Sergestes arcticus, Stebbing, 1905. 

 Sergestes arcticus, Hansen, 1908. 



The carapace is laterally compressed and more than half the 

 length of the abdomen, excluding the telson. Dorsally it is 

 rounded and produced anteriorly to a very short pointed crest 

 or rostrum (fig. 18) which only reaches as far as the basal 

 articulation of the eyestalks. Close to the anterior margin 

 there is a small but well marked ocular spine situated on a 

 short carina; there is also a very prominent hepatic spine. 

 The gastro-hepatic groove is rather deeply cut and extends 

 light over the dorsum of the carapace; the cardiac groove is 

 almost obsolete, but that which defines the superior limit of 

 the branchial region is strong and well-marked. The anterior 

 margin of the carapace is straight on either side of the rostrum 

 and does not protrude forwards as it does in S. similis. 



The third and fourth abdominal somites are slightly 

 flattened above ; the remainder are dorsally smooth and 

 rounded. The sixth somite is deep; it is usually about two 

 and a half times the length of the preceding somite, but in 

 very large specimens is sometimes rather shorter. The telson 

 is shorter than both uropods and is about two-thirds the length 

 of the sixth somite ; as in the case of S. rohustus, it is sulcate 

 above, with a pair of dorso-lateral carinae and a fringe of setae 

 along its inferior margin. 



The eyes (fig 13) are long and slender ; the cornea is round 

 and wider than the stalk. View^ed dorsally they are strikingly 

 different from those of the preceding species, for the corneal 

 portion is not much more than one-third the length of the 

 \\hole eye. 



The joints of the antomular peduncle (fig. 13) also differ 

 widely from those of S. rohustus. The basal segment is long, 

 and considerably narrowed distally ; it is deeply hollowed for 

 the reception of the e}^^ and the lateral process is represented 

 by an obscure notch in the outer margin. The second and 

 third joints, which, taken together, are about as long as the 

 basal segment, are very slender. The ultimate is rather 

 longer than the penultimate and is about five times as long 

 as wide. The lower flagellum of the male (fig. 15) is similar 



