SURFACE COPEPODA OF THE GULF OF MANNAR. 243 



pair of thoracic appendages ; and on the posterior thoracic 

 margin, in most cases, there are two small spines situated 

 dorsally, though in some instances as many as three are 

 present, whereas in A. erythrsea there is only one. 



Associated with these males in the present collections were 

 numerous females. 



?. Total length, 1-2 mm. 



Proportional lengths of cephalo -thorax and abdomen, 14 : 3. 



The head and first thoracic segment are separate, but the 

 last two thoracic segments are fused. The posterior thoracic 

 margin bears a large lateral spine, as A. erythrxa, and one, 

 sometimes two, small spines dorsally. The rostrum consists 

 of a pair of slender spines. 



The abdomen consists of three segments having, with the 

 f ureal rami, the following proportions : — 7 : 3 : 2 : 3. The first 

 segment is armed near its posterior border with a pair of small 

 spines dorso -laterally ; the second segment is devoid of spines. 

 The furcal sette are all of the same thickness, but the second is 

 somewhat longer than the others. 



The first antenna, when folded back, reaches to the end of 

 the first abdominal segment. It consists of eighteen joints, 

 having the following proportions : — 



Segments : 1. 2-4. 5-6. 7-8. 9-10. 11. 12-13. 14. 15-16. • 

 49 81 35 22 97 51 111 57 92 



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



62 57 49 46 57 32 51 38 13 



The first joint bears a long straight spine on its anterior 

 aspect, and two small spines posteriorly ; the second joint 

 bears a large curved hook on its posterior border ; and the 

 fourth joint is armed with two small spines posteriorly. 



The second ayitenna is as figured. 



The first fair of swimming legs consist of a basal portion 

 and two-jointed exopodite and endopodite : exopod 1 has a 

 fine seta-like marginal spine ; exopod 2 bears three margin 

 spines, the proximal of which is long and stout and reaches 

 well beyond the end of the terminal segment, while the distal 

 two are slender and seta -like ; the end spine is slender and in 

 length nearly equals the whole exopodite. 



