MADEIEAN GROUP. 187 



Helix Albersii, Lowe, Proc. ZooL Soc. Loud. 192 (1854) 

 Bulwerii, 7., Alb., Mai. Mad. 24. t. 4. f. 16-18 (1854) 

 Bulweriana, a., Paiva, Mon. Moll. Mad. 95 (1867) 



Habitat Portum Sanctum ; in montibus vulgaris, una cum 

 H. Bulwerii saepe degens. 



Although they have been generally much confused inter se, 

 the present Helix and the H. Bulwerii, which live in company 

 on the mountains of Porto Santo, are nevertheless very readily 

 separated when once their diagnostic features are fairly grasped ; 

 and as the latter (out of many hundred examples which I have 

 inspected) appear practically quite invariable, I scarcely see 

 how we can refuse to accept the conclusions arrived at by 

 Mr. Lowe in regarding the two as specifically distinct. At any 

 rate, as he has published them, and has defined their characters 

 with great precision, I will not undertake to suppress as a 

 species either the one form or the other ; and more particularly 

 so, since my own experience inclines me to think that they are 

 as easily recognizable as any two members of a topographical 

 assemblage can be which are closely allied. 



The H. Albersii is, on the average, a little smaller and paler 

 in colouring than the H. Bulwerii, its under-region (which is 

 more convex) being of a clearer yellowish- or olivaceous-brown, 

 whilst the upper one is not so dark, more evidently unifasciate, 

 and gradually ochreous outside the aperture ; its umbilicus is a 

 little less cylindrical; its keel is not quite so prominent or 

 tectiform; its spire is not so cupola-shaped, or obtuse; its 

 surface is somewhat less densely granulate; and its aperture, 

 which is less angulate in the middle and has the upper margin 

 of the peristome more curved, is appreciably deflected (instead 

 of being quite horizontal) in front. The entire shell, too, is a 

 trifle more solid, or less fragile. Its distinctions from the De- 

 sertan H. Lyelliana have already been pointed out. 



It is chiefly on the higher mountain-slopes of Porto Santo 

 that the H. Albersii and Bulwerii are to be met with ; and 

 although they are pretty general at a tolerable altitude, I have 

 usually observed them in greater profusion on the ascent of the 

 Pico do Facho than elsewhere, a district in which they were 

 obtained in large numbers by Mr. Lowe and myself during 

 April and May of 1855. 



Helix Bulwerii. 



Helix Bulwerii, Wood, Suppl. t. 8. f. 82 (1828) 

 Bulveriana, Lowe, Cambr. Phil. S. Trans, iv. 44. t. 5. 



f. 11 (1831) 

 Bulweriana, Pfeiff., Mon. Hel i. 208 (1848) 



