MADEIRAN GROUP. 181 



with the umbilicus more contracted above, but broader and more 

 cylindrical within, — its sides (much as in the var. attrita) being 

 more abruptly, or more suddenly and perpendicularly, scooped- 

 out. 



V. attrita, Lowe. 



Helix tectiformis, Wood [nee Soiv., 1824], Suppl.t. 8. f. 83 

 (1828) 

 „ polymorpha, S, attrita, Loiue, I. c. 55. t. 6. f. 14(1831) 

 „ attrita, Lowe, Ann. Nat. Hist. ix. 116 (1852) 

 „ „ Pfeig., Mai. Blcitt. 89 (1852) 

 „ „ Lowe, Proc. Zool. Soc. Lond. 188 (1854) 

 „ polymorpha, var. /c.. Alb. I. c. 27. t. 6. f. 12-15 (1854) 

 „ attrita, Paiva, I. c. 88 (1867) 



Habitat Portum Sanctum ; in monte ' Pico d'Anna Ferreira ' 

 dicta praecipue occurrens. Semifossilis in Campo de Baixo 

 rarissime exstat. 



Amongst the numerous phases of the H. polymorpha, the 

 present one (which is peculiar to Porto Santo) was selected by 

 Pfeiffer as specifically distinct ; and certainly the structure of its 

 umbilicus and aperture might well seem at first sight to give it 

 a greater claim for separation than some of the others. Yet I 

 am persuaded that it has no more right, in reality, to be thus 

 treated than any of the rest, — its umbilicus (as regards the sin- 

 gularity of its form) merging so completely into the ordinary 

 shape which obtains in the ' X,. discina ' and its allies that several 

 examples which are now before me might be assigned almost 

 equally to either modification ; whilst the thickening witliin its 

 somewhat more angular apertm-e is merely the same thing, only 

 a little more pronounced, as what we observe in several of the pre- 

 ceding aspects of the species. Indeed the umbilicus of the ' fx. 

 Gomesiana,'' although a trifle wider and more cylindrical, differs 

 very little indeed from that of the present variety, — partaking 

 more of the attrita- than of the cZisc wia-pattern. 



Apart from its contracted and abruptly, or suddenly, exca- 

 vated umbilicus (the result, in part, of the somewhat unnatu- 

 rally inflated base of its ultimate volution), the present shell is 

 extremely solid, acutely carinate, and lenticular, with its volutions 

 greatly flattened, and its surface rather powerfully granulate both 

 above and below. Its aperture (which is much incrassated 

 within) is rather angulated, or subtriangular, in outline, the 

 margins of its peristome being wide apart, and almost uncon- 

 nected by an intervening lamina. Its colour is much that of 

 the ' X. discina ' the surface being either fasciate or efasciate be- 

 neath, but obscurely marbled above with brownish and whitish 



