198 SPOLIA ZEYLANICA. 



posterior margin, and the posterior thoracic margin on the 

 left side is produced backwards ia a rectangular projection ; 

 but a study of numerous examples from various localities in 

 the Indian Ocean and Bay of Bengal has shown that these 

 characters are subject to very considerable variation. As 

 regards the spinulation of the abdominal segments, many 

 specimens possessed spines only on one of the segments, while 

 in some cases spines were absent altogether. Agam, in 

 numerous examples the posterior thoracic margin formed 

 almost a uniform curve, with a very slight rounded projection 

 towards the ventral side ; in other cases this prominence was 

 more marked and formed a somewhat triangular prominence, 

 while in a few cases the t^^pical projection was present. 



In this species, as in U. vulgaris, it would appear that there 

 are three forms of the posterior thoracic margin, which are 

 quite distinct from one another, and a close examination of a 

 large number of specimens has failed to show any correlated 

 change, 



Undestula DARWEsri, var. caroli (Giesbrecht). 



Calanus caroli, Giesbrecht, 1888, p, 331. 



Giesbrecht, 1893, p. 91. PI. VIII., fig. 36. 



(J, Wolfenden, 1905, p. 994. PI. XCVII,, 



fig. 41. 

 Undinula caroli, A. Scott, 1909, p. 18. 



This form was first described by Giesbrecht {loc. cit., 1888), 

 who considered that it was a distinct species. Wolfenden 

 {loc. cit., 1905) obtained examples from the Maldive and 

 Laccadive Archipelagoes, and associated with these were 

 several females, which he considered to be the hitherto - 

 unknown female. According to his brief description these 

 forms were distinguished from the female Undinula darwini 

 by the absence of teeth on the distal portion of the margin of 

 exopod 3 in the second and third pairs of swimming feet, and 

 by the presence of a few fine spines on the first basal of the 

 first pair. The absence of the marginal teeth separates these 

 females from the present form, in which these teeth invariably 

 occur exactly as in U. darwini, and the fine spines on the 

 first basal of the first leg is a character that I have found 



