MADEIRAN GROUP. • 185 



Helix Lyelliana, Loive, Proc. Zool. Soc. Lond. 191 (1854) 

 „ Bulwerii, l3.. Alb., Mai. Mad. 24. t. 4. f. 1 9-22 (1854) 

 „ Lyelliana, Paiva, Mon. Moll. Mad. 93 (1867) 



Habitat Desertam Grandem ; in promontorio alto graminoso 

 occidentali 'Pedragal' (aut, sec. Paiva, 'Ponta dos Castan- 

 heiros') dicto, sat vulgaris sub lapidibus. ' Var. /3. (/i(/as' ad 

 Feijaa Grande invenitur. 



A rather large and sharply keeled Helix which has been 

 found hitherto only on the Deserta Grande, where it was first 

 detected by myself and the late Eev. W. J. Armitage during 

 January of 1849, and where, in company with Mr. Lowe, I 

 again met with it in June 1855. We obtained it only on the 

 lofty western promontory known, I believe, as the ' Pedragal ' 

 (but cited by the Baron Paiva as the Ponta dos Castanheiros), 

 where it was tolerably common on the open grassy slopes 

 beneath stones ; but there is a larger phasis of the shell (the 

 ' var. /3. gigas ' of this catalogue) which was collected for us at 

 the time in an almost inaccessible spot fuxther to the south, on 

 the eastern side of the island, called the Feijaa Grande. The 

 Baron Paiva, after speaking of its habitat, remarks briefly ' sub- 

 fossilis rarior ;' but as there is no record hitherto of a subfos- 

 siliferous deposit on the Central Deserta, there is a rashness 

 about this short observation which inclines me to suspect that 

 the Baron was not sufficiently accurate in his data, and that he 

 probably mistook some examples which were old, bleached, and 

 decorticated for semifossilized ones. 



In their general aspect and colouring the Desertan H. 

 Lyelliana and the Porto-Santan H. Alberaii and Bidwerii have 

 a good deal in common ; but I think that they are nevertheless 

 quite as well separated inter se, by a number of small but 

 constant and readily appreciable characters, as could reasonably 

 be expected with species which belong to the same topographical 

 assemblage, and which are naturally therefore allied ; and I 

 consequently do not agree with Dr. Albers, who professed to see 

 nothing about them to indicate more than races of a single type. 

 Of course it is quite possible to take that view ; but those who 

 adopt it are at least bound to be consistent with their own 

 principles, and to apply the same synthetic treatment (which 

 Albers certainly has not done) to a host of other forms which 

 are similarly circumstanced, and the non-recognition of which 

 would create incalculable confusion, and render all our specific 

 limits a matter of mere speculation and caprice, It is true 

 that this method of dealing with closely related forms is at 

 times unmistakeably forced upon us ; but I will only add, that 

 the case in question is by no means analogous to that of the 

 numerous modifications of the H. polymorpha, — most of which 



