346 



DISCOVERY REPORTS 



Distribution. Pfeffer's and Tattersall's specimens came from South Georgia, as do 

 those in the present collection. 



30. Serolis platygaster, n.sp. (Figs. 18, 19). 



Occurrence. St. 146: 53° 48' 00" S, 35° 37' 30" W, 728 m.; i adult $. 



Description. The specimen (Fig. 18) measures 33 mm. in length and 27 mm. in 

 greatest breadth ; it is broadly ovate in outline and compact in form. The head is broadest 

 anteriorly and widens in front of the eyes, 

 the distance between the eyes being three- 

 fifths of the length of the anterior margin. 

 A small but distinct rostrum is present ; a 

 short distance behind it is a transverse ridge 

 which meets the boundary of the head 

 midway between the eyes and its anterior 

 margin. On either side of the rostrum, 

 the anterior margin is excavated for the re- 

 ception of the base of the antennule and a 

 groove running within the margin extends 

 laterally to the sides of the head. Behind 

 the transverse ridge, and between it and 

 the eyes, the middle portion of the head is 

 convex, whilst the area between the eyes 

 is also raised and divided into two large 

 rounded prominences, the posterior mar- 

 gins of which are better defined than the 

 anterior. In an anterior position between 

 these prominences is a small triangular 

 area, with its apex directed backwards. 



Fig. 18. Serolis platygaster, n.sp., cJ: x 4- 



which is more deeply pigmented than is the rest of the body. The eyes are very small 

 in proportion to the size of the body, postero-lateral in position, about a third of the 

 length of the head, and very narrow ; they contain black pigment. 



As in all Serolidae, the second thoracic segment is united with the head. The lateral 

 portion bears a low ridge extending from near the posterior angle of the eye ; it runs 

 first in a transverse direction outwards, and then branches, with one branch curving 

 forwards and disappearing on the antero-lateral margin of the head, the other curving 

 backwards, running almost parallel with but some distance from the margin of the 

 cephalosome, and disappearing near the posterior border. The third, fourth, and fifth 

 thoracic somites are sub-equal, slightly keeled, with the fifth somite raised near its 

 posterior margin into a small median dorsal protuberance. The sixth and seventh 

 somites are sub-equal, together equal in length to the preceding somite: the posterior 

 sutures of the terga of both somites are absent for a short distance on either side of the 

 mid-dorsal line, so that for a short distance they are fused with each other and with the 



