110 TEST ACE A ATLANTIC A. 



Habitat Maderam, et Portum Sanctum, semifossilis ; in 

 calcareis copiossissime occurrens. 



The present Helix is one of the most abundant of the sub- 

 fossil species, both at Canifal in Madeira and throughout the 

 calcareous deposits of Porto Santo ; and (as in the case of the 

 H. Loivei, when contrasted with the portosanctana) there has 

 always been a question as to whether it represents anything 

 more than the former aspect of the present H. punctulata, 

 Sow. The same observations which I had occasion to make 

 under the H. Lowei will apply here, for I believe that the 

 problem is simply imsolvable, and that it must be decided (so 

 far as that is possible) by each naturalist for himself, — in accord- 

 ance with the exact views which he may happen to entertain of 

 the breadth, and character, of specific variation. 



I am content, for my own part, to cite the H. Boivdichiana 

 as distinct from the punctulata, — first, because it has been 

 generally so acknowledged in the more recent monographs ; 

 secondly, because we have no certain intermediate links of 

 statvire to connect the two (otherwise very similar) forms ; and, 

 thirdly, because in at any rate Madeira proper, where it abso- 

 lutely swarms in a subfossil condition, the H. punctulata does 

 not appear even to occur ; — for although it is of course possible 

 that the H. Bowdichiana may have ceased to exist ivithout 

 initiating a more modern depauperated substitute, yet there 

 seems no reason why it should have done so if the contrary be 

 assumed to have been so eminently the case in Porto Santo that 

 the H. punctulata is now quite as abundant (in that island) as 

 the Boivdichiana ever could have been while the era of the 

 subfossil forms was at its height. Moreover in Porto Santo 

 the two shells, during that particular epoch, lived side-by-side, 

 — although the smaller one (or punctulata), which has become 

 absolutely universal, was then manifestly rare, whilst the larger 

 one (or Boivdichiana), which was then everywhere dominant, 

 has passed entirely away. But if it be replied to all this that 

 the H. Bowdichiana might properly die out in both islands, 

 and yet leave a depauperated progeny in only one of them, I 

 may further remark that on the Southern Deserta the ' depau- 

 perated progeny ' (so-called) occurs without the faintest trace of 

 its ever having possessed a more highly developed progenitor, — 

 the H. punctulata, being rather common on that remote rock 

 (both in a recent and a subfossil condition), without there being 

 any indications in the muddy deposits of its surface that the 

 Bowdichiana had at any time an existence there. So that, 

 from whatever point of view we look at it, the two forms in 

 question would seem to have been originally distinct. 



Apart from its more thickened and nearly colourless, pallid 



