290 DISCOVERY REPORTS 



than long, rounded, ending posteriorly in a fairly large median acute spine; three 

 carinae are present on its dorsal surface, and its lateral margins are not toothed. 



Beddard (1884 b, p. 32) remarks : "it seems to me, from the above quoted description, 

 that it is probably more nearly related to Serolis scJiythei". I agree with Beddard that 

 this may be so. This view is supported by the fact that the distribution of S. serrei agrees 

 with that of S. schythei and differs from that of S. trilobitoides. The description of the 

 species is so brief that it is impossible to make any definite statement with regard to its 

 exact systematic position.] 



6. Serolis polaris, Richardson (Figs. 4 c-f; Plate XIV, fig. 2). 



Serolis polan's, Richardson, 191 1, pp 396-8, fig. i ; Nordenstam, 1933, p. 58. 



Diagnostic characters. This species was instituted to contain six specimens, all of 

 which were said to be females. Through the kindness of Prof. Ch. Gravier, of the 

 Museum d'Histoire Naturelle, I have been able to examine the type specimen and find 

 that it is undoubtedly a male ; for although it is immature the appendix masculina on the 

 second pleopod is quite well developed. This specimen measures 19 mm. in length and 

 21 mm. in breadth. The measurements given by Richardson are presumably those of a 

 female and are length 22 mm. and breadth 22 mm., so that as in so many species of this 

 genus the male is broader in proportion to its length than is the female. 



The head is broader than long, with its broadest portion on a level with the eyes, which 

 lie in a posterior position just within the lateral margins. The eyes are reniform in shape 

 and are less prominent and less deeply pigmented than those of S. schythei, Liitken. 



The body (Plate XIV, fig. 2) bears a close resemblance to that of S. schythei, although 

 it is slightly less flattened. As in that species the posterior margin of the free thoracic 

 somites is produced backwards to form a small median spine, that of the fifth somite 

 being the largest. The coxal plates of the free thoracic somites have their postero-lateral 

 angles acutely produced backwards. The first four pairs are separated from their re- 

 spective somites by sutures, and just within the suture, on either side, the tergum is 

 raised into an angular prominence. The coxal plates of the seventh thoracic somite 

 extend backwards to the postero-lateral angles of the terminal segment, the pleural 

 plates of the second abdominal segment to the end of the terminal segment and those 

 of the third segment to about the middle of the segment. The posterior margin of each 

 of the abdominal segments is produced to form a median tooth similar to those of the 

 thoracic somites. 



The terminal segment is roughly hexagonal in outline, with both the anterior and the 

 posterior angles very obtuse, and with the sides shghtly converging and terminating in 

 an acute tooth on either side, into the angle of which the protopodite of the uropod is 

 inserted. 



The dorsal surface is furnished on either side with a curving ridge, situated close to 

 the anterior and lateral margins of the segment ; behind this, arising from a small flat 

 angular process, one on either side of the base of a large median spine, is a second ridge 

 which runs obliquely outwards to terminate in an angular process near the postero- 



