3i8 DISCOVERY REPORTS 



(9) The distribution of S. convexa and S. goiidichaiidii is somewhat similar. The 

 former occurs off the coast of the Argentine Republic and around the Falkland Islands ; 

 the latter has been recorded from the shores of South America and off Valparaiso. The 

 only record of S. laevis is the South Sandwich Islands, a locality farther east than any 

 of those recorded for the two former species. 



Nordenstam, 1933, includes S. laevis as a synonym of S. convexa. 



I'j. Serolis gerlachei, Monod. 



S.gerlachei, Monod, 1925, p. 299; 1926, pp. 36, 37, text-figs. 35-7. 



Only one specimen of this species, an immature male, has so far been recorded, and 

 I wish to express my gratitude to Dr von Straelen of the Musee Royal d'Histoire 

 Naturelle de Belgique for allowing me to examine it. 



Diagnostic characters. The body is longer than broad, strongly arched and with a 

 median longitudinal keel; it measures 10 mm. in length and 8 mm. in greatest breadth. 

 The breadth of the head is about equal to its length, excluding the end of the median 

 spine. The head is broadest anteriorly ; the antero-lateral angles are produced beyond 

 the anterior margin, which is excavated on either side of a minute median rostrum for the 

 reception of the antennules. The antero-lateral angles are marked off by a transverse 

 ridge which extends across the head immediately behind the base of the rostrum ; the 

 area behind this ridge and between the anterior ends of the eyes is raised, and is separ- 

 ated by a slight groove from the raised area between the eyes. The latter area is divided 

 into two lateral oval prominences and a median area which is produced backwards as 

 a long acute spine extending to about the middle of the second free somite. The eyes 

 are reniform and pigmented. 



The first three free somites (3rd-5th) are sub-equal in length. The third has its 

 posterior margin produced into a small median spine ; the fourth and fifth free somites 

 are together equal in length to the first free somite, and are without spines. The coxal 

 plates of all the thoracic somites are compact and those of the first three free somites are 

 separated from them by sutures. The coxal plates of the seventh thoracic somite extend 

 for a short distance beyond the bases of the uropoda and farther than the pleural plates 

 of the second and third abdominal segments, the latter of which are a little longer than 

 the former and reach to the bases of the uropoda. The terga of the three abdominal 

 segments are each produced posteriorly into a small median dorsal spine. 



The terminal segment is roughly pentagonal in outline, slightly longer than broad, 

 with a sub-acute posterior extremity. On its dorsal surface, in an anterior median 

 position, is a small raised triangular area with its apex directed backwards ; this is con- 

 tinuous with a median carina which extends to the posterior extremity of the segment. 

 On either side, arising from the angle of the base of the triangle, is another carina which 

 runs obliquely outwards and terminates in a spine some distance within the lateral 

 margin, just behind the level of the base of the uropod. Midway between this and the 

 median carina, and running parallel with the latter, is a third carina which starts an- 

 teriorly a little behind the apex of the triangular area and terminates posteriorly a short 



