1 68 COOKE : ON THE GENUS CUM A. 



It is necessary to state distinctly what Tryon's views are 

 with regard to the first new member of this list, viz. : purpuroides 

 d'Orb. In vol. ii., p. 200, he writes, ' This well-known species, 

 inhabiting the West Coast of Central and South America, is 

 said to have a fusoid operculum ; it will therefore be described 

 and figured in vol. iii. Conchologically, the species is very 

 closely allied to C. kiosqiiiformis Duel.' Referring to vol. iii., 

 p. 109, we find ' Afelofigena fusiformis Blainv. This shell is 

 apparently very closely related to C. kiosqinfor?ms, but the 

 operculum, according to d'Orbigny, is not purpuroid. The re- 

 semblance, conchologically, is much nearer [to] Cutna than 

 either [to] Melongena or Siphonalia, and I cannot help thinking 

 that the great French naturalist was mistaken as to the oper- 

 culum.' 



Now, this is all a piece of guess-work, of a most unscientific 

 kind. d'Orbigny was perfectly correct in stating that the oper- 

 culum is not purpuroid. We have a specimen in the MacAndrew 

 collection here, whose operculum, though unfortunately imper- 

 fect, is yet quite sufficiently perfect to enable one to state 

 distinctly that the shell which possesses it is not allied to 

 Cu?fia, or even to Piu-pura, in the remotest degree. Perfect 

 specimens with the operculum m situ may be seen at the 

 British Museum. The unguiculate form and terminal nucleus 

 settle at once the question of its non-purpuroid relationship ; 

 whether the affinities of the shell be in the direction of 

 Melo7igena or Fitsus or Siphonalia is another matter, which 

 must wait for an examination of the animal, and in particular 

 of the dentition. Conchologically, too, the difference between 

 the two shells is very marked. The thick ' fibrous-brown ' 

 epidermis of purpuroides is of itself suflEicient evidence that 

 the shell which it envelopes so tightly is not a Purpura. Few 

 Purpuras have a distinct epidermis at all, and none any that in 

 the least degree resembles this. 



It may be added that the locality given by Tryon, on 

 Cuming's authority (St. Elena, W. Columbia), is probably in- 



J.C, v., April, 18S7. 



