MADEIRAN GROUP. 131 



Helix maderensis. 



Helix maderensis, Wood, Ind. Test. Supp. t. 8. f. 84 (1828) 

 „ „ Lowe, Camb. PhU. S. Trans, iv. 48. t. 5. 



f. 22 (1831) 

 „ „ Pfeiff., Mon. Eel. i. 213 (1848) 



„ „ Lowe,Proc.Zool.Soc.Lond. 195 (1854) 



„ „ Alb., Mai. Mad. 29. t. 7. f. 5-10 (1854) 



„ „ Paiva, Mon. Moll. Mad. 51 (1867) 



Habitat Maderam ; in aridis apricis submaritimis, a litore 

 maris usque ad 2000' s.m. copiose ascendens. 



The present Helix may be regarded as the central one, or 

 type, of the little group of forms of this immediate pattern, — 

 combining much the same sculpture as the tosniata, with the 

 smaller size, less depressed spire, and less carinated outline of 

 the compar. It is, however, distinctly, more keeled than the 

 latter, and its sculpture (as already mentioned) is quite dif- 

 ferent, — its upper surface being merely crowded with closely- 

 set costate lines (instead of remote and elevated ridges), some 

 of which are rather larger and paler than the rest, with the 

 addition of a few coarse granules scattered sparingly towards 

 the aperture. Its umbilicus is relatively a trifle narrower than 

 that of either the compar or the tmniata. 



The mere variations of colour, in this and the two preceding 

 species, are scarcely important enough to deserve notice, — the 

 single narrow band with which they are ornamented, both above 

 and below the keel, being occasionally (though not often) so 

 increased in width as to be comparatively conspicuous, whilst at 

 other times, on the contrary, it is nearly, or even altogether, 

 absent. Specimens in this latter condition, which are fre- 

 quently smaller and less developed than the average, would 

 seem to have been mistaken by Albers (as is evident both from 



that even the former belongs to a distinctively Madeiran type, it is much to 

 be regretted that he shoidd not have rejected them in toto from his late 

 volume — as forms (to say the least) of uncertain habitat, and such as ought 

 never to have been introduced into the Catalogue at all. Speaking of the 

 H. tceniata, he says : ' Cette espece n'a pas ete recueillie dans les Canaries, 

 mais a ete trouvee par M. Terver dans un ballot d'Orseille d'origine inconnue. 

 Sa forme rappelle tellement les especes de Madere, qu'il est bien plus pro- 

 bable quelle appartienne reelement a ce second groupe d'iles, ou se recolte 

 egalement ce lichen.' And of the tiarella he adds : ' Cette espece se tronre 

 rivante et subfossile dans Madere, et il n'est guere probable, vu la difference 

 des deux faunes, qu'elle se retrouve dans les Canaries. Son origine en effet 

 est tout aussi douteux que celui de la tr/'niata, puisque, comme elle, la tiarella 

 ne s'est trouvee dans de l'Orseille de source inconnue.' And he then observes : 

 ' La patrie bien etablie de l'une de ces deux especes donne la clefpowr celle de 

 I 'autre ;' so that, on his own shewing, as he acknowledged one of them to be 

 undoubtedly Madeh'an, the other must have been Madeiran likewise. There- 

 fore why did he not eliminate them immediately? instead of perpetuating, 

 by not doing so, a geographical error. 



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