KEY TO ALL KNOWN SPECIES OF SEROLIS 279 



C. Only the first three free thoracic somites (3rd-5th), separated from their respective coxal 

 plates by sutures. 



L Coxal plates of seventh thoracic somite not extending backwards beyond the pleural 

 plates of the second and third abdominal segments. 



a. Pleural plates of second abdominal segment extending beyond those of third. 

 Terminal segment with well-developed spine in anterior median dorsal line, 

 followed by a median carina extending to its extremity; on either side of median, 

 two lateral oblique carinae terminating in small spines some distance from the 

 lateral margins y. S.gladalts,Tanersal\. 



b. Pleural plates of third abdominal segment extending beyond those of second. 



1. Extremity of terminal segment trifid ; dorsal surface of terminal segment with a 

 median carina and three lateral ones on either side of it. 8. S. septemcaiinafa, Miers. 



2. Extremity of terminal segment fiot trifid; terminal segment broader than long 

 or about as broad as long. 



a. Terminal segment with a well-developed spine in the antero-dorsal line, 

 followed by a median carina. 



(i) Median carina slight, terminating in a spine at some distance from the 

 upturned, pointed posterior extremity; two lateral oblique carinae on 

 either side, terminating in spines ; two inner terminating in a line with the 



end of the median carina g. S. kempt, n.sp. 



(ii) Median carina extending to extremity of segment, with two lateral oblique 

 carinae on either side of it, each terminating in a small spine some distance 



from the lateral margins 10. 5. /)o/iVa, Pfeffer. 



^. Terminal segment without well-marked dorsal spine in an antero-median 

 position. 



(i) Uropoda broad and extending beyond the posterior extremity of the 

 terminal segment ; body oval in shape and without spines 



U.S. elliptica, n.sp. 



(ii) Uropoda not broad and extending beyond the posterior extremity of the 

 terminal segment; cephalosome with dorsal posterior margin produced 

 backwards to form a median spine reaching to near the middle of the first 

 free (3rd) thoracic somite; spine less pronounced in the female 



12. S. exigiia, Nordenstam. 



IL Coxal plates of seventh thoracic somite extending beyond the pleural plates of the 

 second and third abdominal segments. 



a. Pleural plates very short, not extending beyond the anterior margin of the terminal 

 segment. 



1. Terminal segment with three dorsal carinae, the median one of which is not 

 mterrupted in the middle: lateral carinae following the outline of the segment 

 at some distance within it and meeting the central one at its posterior 

 extremity 13. 5. raww/a, Lockington 



2. Terminal segment with three dorsal carinae, the median one of which is inter- 

 rupted in the middle. 



a. Lateral carinae well developed and ending in spines; terminal segment 



narrowing posteriorly ; body pear-shaped ... 14. 5. co«wxa, Cunningham^. 



(8. Lateral carinae are well marked ; terminal segment almost circular in outline ; 



body broadly oval 1^. S. gaudkliauJn, And. et Ed-w. 



y. Median and lateral carinae almost obsolete ... 16. 5. /aew, Richardson. 



1 S. plana, Dana, is probably identical with S. convexa. 



4-2 



