DESCRIPTION OF SPECIES 327 



44 mm. in breadth. The colour of living specimens was pale horn, blotched and mottled 

 with a darker colour which varied from maroon to pale terra-cotta. 



The head is shield-shaped and almost identical with that of S. cornuta, Studer: it is 

 broadest anteriorly, with the anterior margin excavated on either side of the small 

 median rostrum for the reception of the antennules ; immediately behind this is a trans- 

 verse ridge extending laterally to the sides of the head. In front of and between the eyes 

 is a square raised area with its posterior margin slightly concave, the two angles being 

 somewhat produced backwards. The area between the eyes, which, except anteriorly, is 

 separated from them by deep grooves, is convex and is divided posteriorly into a median 

 and two lateral areas, each of the latter being in the form of a flattened, somewhat oval 

 enlargement, produced backwards into a very small spine. The median area is produced 

 into a narrow four-sided plate with a small dark tubercle in its centre ; this lies between 

 and rather behind the two lateral enlargements. The eyes are reniform in shape, rather 

 narrow, and containing black pigment. 



The lateral portion of the cephalosome is divided on either side into an anterior and 

 a posterior portion by a well-marked transverse groove, which extends outwards from 

 a point near the postero-lateral margin of the eye to the lateral margin. A further 

 ridge on the anterior portion arises near the end of the anterior transverse ridge of the 

 head. 



The thoracic somites increase in length from the third (first free) to the fifth ; the fifth, 

 sixth, and seventh are sub-equal. Each somite has well-developed coxal plates, those 

 of the third, fourth and fifth being separated by sutures. The plates are somewhat 

 sickle-shaped, with the terminal portion from the articular process outwards curved 

 backwards, and outwards, following closely the outline of the preceding one (cf. 

 S. cornuta, Studer). The coxal plates of the seventh thoracic somite are produced back- 

 wards to a point half-way between the attachment of the uropod and the end of the 

 terminal segment, reaching slightly beyond the pleural plates of the abdominal seg- 

 ments ; the lengths of these plates are almost the same in both sexes. 



The first three abdominal segments are sub-equal (Fig. 13 a), with the sterna each 

 bearing a median spine, increasing in size from before backwards; these are well de- 

 veloped in the female, but only slightly in the male. The pleural plates of the second and 

 third abdominal segments extend backwards almost as far as the coxal plates of the 

 seventh thoracic somite ; those of the second segment are slightly the longer. The outer 

 margins of the coxal and pleural plates are minutely though not so deeply serrated as 

 those of S. cornuta. 



The terminal segment (Fig. 13 a) is pentagonal in outline, ending posteriorly in a 

 spiniform process which is not as long or acute as the corresponding one in S. cornuta. 

 The segment is broader than long, that of the largest specimen measuring 18 mm. in 

 length (including the terminal spiniform process of 2 mm.) and 19 mm. in greatest 

 width. On the dorsal surface is a longitudinal median keel bearing five or six recurved 

 teeth ; the first of these is the largest, but none are as large as those in a similar position 

 in S. cornuta. The area in front of the first tooth is raised and bears two small spines, 



