206 SPOLIA ZEYLANICA. 



I have met with numerous examples of this male form, and a 

 study of its structure has convinced me that it is the true male 

 of P. aculeaius. 



I give below a description of these individuals : — 



cJ. Total length, 1-2 mm. 



The abdomen and cephalothorax have the relative pro- 

 portions 1 : 2 "6. The head and first thoracic segments are 

 fused, as are also the fourth and lifth thoracic segments, 

 though in the latter region traces of the original line of division 

 are distinctly visible ; the posterior thoracic margin is rounded. 



The abdomen consists of five segments, having, with the 

 f urea, the following proportional lengths : — 



13 : 27 : 20 : 19 : 17 : 12. 



The furcal rami are symmetrical, and the proportions of 

 length to breadth are 12 : 9. 



The First Antenna. — As in the case of the adult male of 

 P. parvus, so here also we find that the basal segments of the 

 antenna become fused together into three joints — the first 

 and second, the third to the sixth, and the seventh and eighth 

 segments respective!}^ being fused. The proportional lengths 

 of the joints are as follows : — 



Segments : 1-2. 3-6. 7-8. 9. 10. 11. 12. 13. 14. 15. 

 117 157 68 20 26 28 31 40 40 40 



Segments : 16; 17. 18. 19. 20. 21. 22, 23. 24. 25. 

 43 43 46 46 46 46 43 49 40 31 



The antenna when folded back only reaches to the end of the 

 abdomen. 



Second Antenna. — This appendage exactly resembles those 

 of the sexually mature males of P. iMrvus {vide Giesbrecht. 

 1893, PI. IX., fig. 23) and P. serratipes (ride Sewell, 1912, 

 PI. XV., fig. 7). As I have already pointed out, the nipple- 

 like termination of the exopodite is a sexual character 

 developed in adult males in the three genera Paracalanus, 

 Acrocalanus, and Peizocalnnus Hoc. cit., 1912, p. 336). 



The mouth pirts are similar to those of other adult males 

 of the same sjenus. 



