MADEIRAN GROUP. 173 



mis hinc inde vulgatissima. Semifossilis ad Canical Maderaa 

 parcissime sed in summo Desertae Australis copiosius invenitur. 



While the last (or normal) state of the H. polymorpha is 

 characteristic of a limited district in the extreme east of Madeira 

 proper, the present one makes its appearance in many parts of 

 the eastern and northern coast of the same island, extending like- 

 wise .to the Desertas, on the whole three of which it occurs, 

 though more particularly on the central or larger one. The Ma- 

 deiran examples however are not usually quite similar to those 

 of the Desertas, being, on the average, a little more sharply 

 keeled and more coarsely granulated ; and they are generally too 

 a trifle thinner (or less solid), and not so highly coloured : indeed 

 I possess a series of them from the Ponta de Pargo (perhaps 

 somewhat exceptional) which are nearly devoid of markings. 



Although extremely variable in the elevation of its spire, the 

 ' 0. salebrosa ' is considerably less conical than the (so-called) 

 type, it being altogether flatter and more lenticular; but the 

 Madeiran phasis of it is, I think, quite as strongly asperated as 

 the latter with powerful granules. The Desertan specimens are 

 usually less coarsely granulated, particularly above, and their 

 keel is a little more obtuse ; but both of these features are subject 

 to considerable variation. As for the mere development of the 

 bands (which are for the most part more conspicuous in the De- 

 sertan race than in that from Madeira), hardly two examples have 

 them precisely alike. 



The ' /8. salebrosa ' (which is so common on the Desertas, par- 

 ticularly on the central island) was found by Mr. Lowe in Madeira 

 proper, namely on the Larana promontory below Porto da Cruz, 

 and at the Ponta de Pargo ; and it occurs likewise between Ma- 

 chico and Sta. Cruz. In a subfossil condition it is not uncommon 

 on the summit of the Southern Deserta, but extremely rare in the 

 calcareous deposits near Canical. 1 



y.porompkala, Lowe. 



Helix polymorpha, S.,P/eiff., Mai. Bldtt. 81 (1852) 



poromphala, Lowe, Ann. Nat. Hist. ix. 116 (1852) 

 senilis (pars), Id., Proc. Zool. Soc. Loud. 189 (1854) 

 polymorpha, var. S., Alb., I. c. 26. t. 5. f. 19, 20 (1854) 

 var.. (subv. 1), Paiva, I. c. 84 (1867) 



Habitat tres Desertas ; prsecipue in insulis Boreali et Australi 

 congregans. In Deserta Australi semifossilis quoque reperitur, 



1 As regards the synonymy of this shell, I may add that the name 'senilis' 

 having been preoccupied by Morelet during the preceding year to that in 

 which it was employed by Mr. Lowe, it became necessary for the latter to 

 propose a fresh one, which he consequently did in 1862. 



