164 TEST ACE A ATLANTIC A. 



Helix turricula, Pfeiff., Mon. Hel i. 190 (1848) 



Lowe, Proc. Zool. Soc. Lond.'ISQ (1854) 



Alb., Mai. Mad. 37. t. 9. f. 11-13 (1854) 



Paiva, Mon. Moll. Mad. 47 (1867) 



Habitat in insula parva ' Ilheo de Cima ' dicta, juxta Portum 

 Sanctum (nee alibi) ; sub lapidibus magnis congregans. 



This is one of the most beautiful, and distinct, of all the 

 land-shells of the Madeiran archipelago ; and yet there is not a 

 single species which is more narrowly circumscribed (so far as 

 our united observations have hitherto shewn) as regards its area 

 of distribution, the little rocky islet known as the Ilheo de 

 Cima, at the south-eastern extremity of Porto Santo, being 

 apparently its only habitat. In that particular locality how- 

 ever it abounds, where it is to be met with (often in clusters) 

 beneath the large blocks of basalt which lie scattered on (more 

 especially) the western slopes. Under such circumstances it 

 has been taken in profusion by Mr. Lowe and myself, on various 

 occasions, as well as by Senhor Moniz and other naturalists ; 

 but I have never been able to detect any traces of it in a sub- 

 fossil state on the mainland, not even at the Zimbral d'Areia, 

 which is exactly opposite to (and but narrowly separated from) 

 the Ilheo de Cima, nor in the muddy accumulations of the 

 subfossiliferous sea-cliff (below the Pico dos Maparicos) to the 

 eastward of the Villa. Hence there is every reason to suspect 

 that it has never existed except on that small and nearly inac- 

 cessible island. Yet so intimate is its relationship with the 

 subfossil H. vermetiformis, which as already stated is par 

 excellence characteristic of the deposits in the direction of the 

 Ilheo de Cima, that it is impossible to resist the enquiry as to 

 whether it. might not in reality be some extreme development 

 of that quondam form, which has been gradually matured since 

 the Ilheo de Cima was permanently separated from the main- 

 land. This question however being merely a speculative one, 

 hardly concerns us here, for no amount of evidence can ever 

 succeed in raising it beyond the atmosphere of probability ; and 

 it may be sufficient therefore to add that the H. turricula in 

 even its most abbreviated phasis (under which guise alone it 

 bears a primd facie resemblance, in its shorter contour, more 

 prominent keels, and somewhat disproportionately widened 

 ultimate volution, to the vermetiformis) differs from its un- 

 questionably near ally in its much more elevated spire (and 

 that too when seen in its most reduced and exceptional con- 

 dition), in its entire surface being very much more finely and 

 closely granulated, and in its umbilicus (which is likewise more 

 concealed by the overhanging edge of the peristome) being less 



