SURFACE COPEPODA OF THE GULF OF MANNAR. 235 



The fourth and fifth thoracic segments are also fused. The 

 posterior thoracic margin is rounded, and is armed with a small 

 spine. The head is furnished with a pair of large eye lenses, 

 and the ventral lens is well developed and of a plum-colour. 

 The rostrum is bifid, and is composed of two slender spines ; 

 there is no rostral lens. The abdomen consists of five segments, 

 having, with the f ureal rami, the following proportional 

 lengths :— 27 : 32 : 32 : 16 : 9 : 38. 



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

 the abdomen ; that on the left side consists of twenty-two 

 jomts, having the following proportional lengths, and for 

 purposes of comparison I also give the lengths of the joints 

 in the female : — 



Segments: 1. 2. 3. 4. 5. 6. 7-8. 9. 10. H. 12. 

 (J ..65 65 15 11 13 26 49 26 23 38 39 

 $ ..81 81 17 13 14 28 50 22 22 36 38 



Segments : 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 

 (J ..36 41 73 73 81 86 54 62 52 41 41 

 $ .. 36 45 66 66 78 81 52 48 50 38 38 



Segments 7 and 8 are partially fused together. The right 

 antenna is modified to form a grasping organ ; it consists of 

 nineteen joints, having the following proportional lengths : — 



Segments : — — — — — — — — 12. 13. 



S ■. 56 75 18 14 13 32 37 42 26 24 



Segments: 14. 15. 16. 17. 18. 19-21. 22. 23. 24-25. 



S .. 40 72 87 70 106 119 89 40 40 



Segments 11, 12, and 13 each bear a minute spine on the 

 anterior surface ; the seventeenth segment bears a curved 

 lamellar plate very similar to that present in L. detruncata ; 

 the eighteenth segment is armed with a lamellar plate carrying 

 a number of fine acicular spines, and the nineteenth segment 

 carries a raised tooth-plate very similar to that of L. detnmcata, 

 but only reaching about three-fourths the length of the 

 segment, not beyond the distal joint as in L. detruncata, nor 

 is it so rounded at its extremity. 



The Fifth Pair of Legs. — ^That on the right side has much the 

 same shape as that of L. detruncata, but the proximal process 

 is not so stout ; the left leg also has a similar structure. 



