178 TEST ACE A ATLANTIC A. 



rally fragmentary and sub-obsolete (being often only traceable 

 as a few detached, transverse, griseous, zigzag streaks and shape- 

 less blotches). 



I. pWvinata, Lowe. 



Helix polymorpha, ^. pulvinata, Loive, I. c. 56. t. 6. f. 16 



(1831) 

 /3., Pfeiff., Mai. Bldtt. 81 (1852) 

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

 „ „ Id., Proc. Zool. Soc. Loud. 188 (1854) 



„ polymorpha, var. /3. Alb., I. c. 26. t. 5. f. 14, 15 



(1854) 

 „ cheiranthicola, a. pulvinata, Paiva, I. c. 49 (1867) 



Habitat Portum Sanctum, insulasque parvas adjacentes ; in 

 aridis apricis calcareis arenosis inferioribus praecipue et copiose 

 congregans. Semifossllis rarissima, sed ad Zimbral d'Areia parce 

 collegi. 



In its somewhat cushion-shaped, basally inflated, ultimate vo- 

 lution and open umbilicus, as well as in its more or less conical 

 or elevated spire and its rather finely and thickly granulated 

 surface, the present race of the H. polymorpha has a good deal 

 in common with the last one ; nevertheless it is a trifle smaller 

 and less acutely keeled, its peristome is more continuous (the 

 upper and lower margins being joined by a much thicker corne- 

 ous process), its whorls are a little more tumid or convex, and its 

 colour is totally different, — the entire shell being more or less 

 pale and (as it were) bleached in appearance, even the darkest 

 examples being seldom more than obscurely variegated above with 

 a few irregular, transverse, brownish markings.' 



The ' t. pulvinata ' is one of the most abundant Helices in 

 Porto Santo, to which island and the adjacent rocks it is peculiar, 

 — occurring more particularly in the driest and most calcareous 

 spots of a low elevation. Thus it often swarms beneath stones in 

 the Eibeira de Cochim and about the sandy edges of the Campo 

 de Baixo, and indeed generally around the Villa ; but it is 

 found likewise at a rather higher altitude. Like most of the 

 modifications, however, of the H. polymorpha, it is decidedly 

 rare in a subfossil condition ; though it was met with sparingly, 

 by Mr. Lowe and myself, at the Zimbral d'Areia and elsewhere. 



' By the Baron Paiva the present Helix is treated as a variety of the 

 If. clwiraittMcola ; but it is difficult to understand on what sin.^le character 

 it can be separated from tlie Discitla group, — its ratlier elevated spire being 

 more than paralleled in tlie typical phasis of the //.^-'('^y/wOTyy/uf, and quite 

 equalled in the ' var. 6. Barbusce.' 



