180 TEST ACE A ATLANTIC A. 



Helix discina, Loivc, Proc. Zool. Soc. Lond. 190 (1854) 

 „ polymorpha, var. i}. 9 Alb., I. c. 26. t. 6. f. 1-3(1854) 

 „ „ var. 8., Paiva, I. c. 86 (1867) 



Habitat Portvtm Sanctum, insulasque parvas adjacentes ; in 

 aridis apricis vulgatissima. Semifossilis multo rarius exstat. 



The 'X. discina'' is one of the most abundant of all the 

 phases of the H. polymorpha, being universal in Porto Santo and 

 on most of the immediately adjacent rocks, — I having- myself met 

 with it on the Ilheo de Baixo, the Ilheo de Cima, and the Ilheo 

 de Ferro. It is a central form which is less easily defined than 

 the generality of others, — partaking, as it does, of the features of 

 many of them ; but it may be described as, on the average, rather 

 flat and lenticular, with the keel sharply pronounced, and the 

 umbilicus (although not large) open and spiral. It is finely 

 granulated both above and below ; its whorls are usually de- 

 pressed, with the suture hardly at all sunken ; the margins of its 

 peristome are wide apart, and nearly unconnected by a corneous 

 lamina ; and its surface, although seldom very brightly coloured, 

 is either fasciate or efasciate below, and more or less obscurely 

 mottled above with darker and paler irregular transverse 

 markings. 



Like most of the modifications of the H. polymorpha when 

 found at all in anything but a recent state, the present one is 

 undoubtedly scarce subfossilized. Nevertheless it has been met 

 with sparingly, by Mr. Lowe, myself, and others, on the Campo 

 de Baixo, as well as at the Zimbral d'Areia. 



fx. Gomesiana, Paiva. 



Helix Gomesiana, Paiva, Journ. de Conch, xiv. 340. pi. 1 1 . 



f. 6 (1866) 

 „ „ Id., I. c. 89. t. 1. f. 5 (1867) 



Habitat ins. parvas ' Ilheos de Nordeste ' dictas, juxta Portum 

 Sanctum ; vulgaris. 



The present modification of the H. polymorpha was obtained 

 by the Baron Paiva, in 1863, from the almost inaccessible rocks 

 off the north-eastern coast of Porto Santo known as the ' Ilheos 

 de Nordeste.' It differs but little from the * \. disci/no, ' ; but 

 having been published by the Baron as a distinct species, it 

 must of necessity be noticed. 



Judging from the types before me, the ' fx. Gomesiana ' is (on 

 the average) a trifle smaller than the ' X. discina,'' and m re 

 thicklv granulated ; its keel is not quite so shaiply expressed ; 

 its volutions are not quite so flattened ; its upper portion i s \ ess 

 variegated, being more darkly and uniformly diffused with a 

 warm reddish-brown tint ; and its' base is more decidedly Op a k e? 



