300 DISCOVERY REPORTS 



lo. Serolis polita, Pfeffer. 



S.poIiia,P{efleT, 1887, p. 8i, pi. ii.figs. 3, 4, pi. iv,fig.4; Richardson, 1906 a, p. 7; Richardson, 1911, 

 pp. 396; Tattersall, 1921, p. 231, pi. vii, fig. 6; Monod, 1931, pp. 26-7; Nordenstam, 1933, 

 pp. 63-5, text-figs. 



Occurrence. St. 371: South Sandwich Islands, 99-161 m.; 2 immature. 



St. WS 25: South Georgia, 18-27 "^■' ' o and 2 immature specimens. 



St. MS 65: East Cumberland Bay, 78 m.; i immature specimen. 



St. MS 66: East Cumberland Bay, 18 m.; 2 ?? (b.), 2 $? (non-b.), 2 3o, and 2 immature. 



St. MS 67: East Cumberland Bay, 38 m.; i immature specimen. 



Diagnostic characters. The largest specimens, both male and female, measure 

 1^-5 mm. in length; the male, as is usually the case, is broader than the female and 

 measures 15 mm. in breadth; the breadth of the female is 13-5 mm. The body is broadly 

 ovate and slightly keeled. 



The head is broadest anteriorly ; its margin is excavated for the reception of the an- 

 tennules, between which it is produced forward as a very small rostrum. On either side 

 of the head a transverse ridge extends from the outer side of the excavation for the 

 antennule to the lateral margin of the cephalosome. The area of the head behind the 

 rostrum is raised, and a short transverse ridge extends across between the anterior 

 margins of the eyes ; immediately behind this is a shallow depression. The area between 

 the eyes is convex and divided into three areas, the two lateral of which appear as some- 

 what obliquely placed oval prominences. The central area is not raised as much as the 

 lateral ones, neither does its straight posterior margin extend back as far : the posterior 

 margins of these prominences are better defined than the anterior, which merge into the 

 general surface of the head. The lateral portion of the second thoracic segment is not 

 divided by a transverse ridge. 



Eyes large, reniform in shape, containing black pigment. 



The third and fourth thoracic somites are sub-equal, the fifth is slightly longer ; the 

 sixth and seventh are together equal in length to the fifth. In the mid-dorsal line each 

 somite is produced into a small spiniform process. The coxal plates are well developed 

 and those of the third, fourth and fifth somites are marked off by distinct sutures. The 

 coxal plates of the seventh somite are only slightly more produced than those of the 

 other somites and do not extend nearly as far backward as do the pleural plates of the 

 second and third abdominal segments. 



Each of the three free abdominal segments bears a short median dorsal spiniform 

 process. The pleural plates of the second and third segments are broad ; those of the 

 third segment are produced backward to the level of the articulation of the uropoda, 

 those of the second to a level a little over half-way between the tip of the coxal plate of 

 the seventh thoracic somite and that of the pleural plate of the third abdominal segment. 



The terminal segment is broader than long, with a well-developed spine in the anterior 

 median dorsal line, followed by a median keel which extends to the extremity. On 

 either side of this keel are two lateral oblique keels, the outer one of which is the longer ; 

 each terminates posteriorly in a small spine at some distance from the lateral margins, 

 which are somewhat flattened. The posterior extremity of the segment is rounded. The 



