64 



NOTE UPON OLIVA GIBBOSA, BORN, AND ITS LIMITS OF 

 VARIATION. 



By J. Cosmo Melvill, M.A., F.L.S. 



Read 8th January, 1904. 



This well-known and very conspicuous mollusc, whose headquarters 

 have been reported as tropical West African,' but which, nevertheless 

 seems to have a wide distribution over a great portion of the extensive 

 Indo-Pacitic province, having been reported from Ceylon, Andaman 

 Islands (Booley), Mauritius (Barclay), Mergui Arcliipelago (Anderson), 

 and the Philippines, may, in its typical form, be described as a broad, 

 massive shell, a tine example measuring a good 3^ inches to even 3^ 

 longitudinally by H inches in breadth, the normal coloration being a 

 livid mottled grey, the broad basal fascicle ochreous, much spotted or 

 suifused with cinereous. When the outer cuticle is removed, the 

 mottled surface shows much more clearly, the colour then being a fine 

 chocolate or sepia. The white spaces are seen to be mostly narrow, 

 long, often triangular or cuneiform, or shaped like the letter L. 



The spire and the whole of the columellar region exhibit an unusual 

 amount of callosity. On the one hand, its nearest approaches, through 

 its most cylindrical variety, are the closely allied 0. nehulosa, Lamk., 

 a species so identical in colour and marking as to suggest a common 

 ancestor, and 0. intricnta, Marrat, by many considered only a variety 

 of nehulosa, Lamk., though to my mind it seems peculiar in its 

 marking. On the other side, the still more massive Olivancillaria 

 BrasUiana, Lamk., from the New World, is nearly allied, but the 

 sutural canaliculations in gibbosa form an undoubted line of 

 demarcation here. 



' Probably on insufficient grounds. 

 Collectiou may not be correct. 



Specimens so labelled in the Cumingian 



