140 TESTACEA ATLANTICA. 



the island) at Feijaa d'Ovelha, and on sea-cliffs at the Ponta 

 de Pargo, in which last-mentioned locality it was first de- 

 tected by Mr. Lowe, during December of 1826. 



In its more or less obliquely-mottled (or streaked) surface, 

 as well as in its rounded, depressed, sublenticular outline, the 

 H. arcta has much the prima facie appearance of the H. lenti- 

 ginosa ; nevertheless, both in its structure and mode of life, it 

 is essentially distinct from that species. Thus it is not only 

 smaller and natter, but altogether more thickened, solid, and 

 robust ; it has a volution less (namely 41, instead of 5) ; its 

 umbilicus, although open and conspicuous, is relatively a trifle 

 smaller and more punctiform ; and it is not only more coarsely 

 costate-striate, but nearly (if not indeed altogether) bald, or 

 free from every trace of minute hair-like lacinise. Its peristome 

 too is more continuous and incrassated, as well as more corneous, 

 whiter, and more recurved ; and (which is its most important 

 feature) it possesses a white, elongate, oblique callosity or tooth, 

 within the aperture on the ventral wall. 



There is, however, a slightly smaller phasis of this shell (the 

 ' var. (B. 'minor ' of Lowe) which is a little thinner in substance 

 and not quite so strongly costate, and in which the ventral tooth 

 is either almost or entirely obsolete. This was first met with 

 by myself, during January of 1849, on the ' Telegraph Hill' (or 

 Pico da Cruz), above the Eace Course, to the westward of Fun- 

 chal, particularly on the slope descending towards the Gror- 

 gulho; and the same form has been found subsequently at 

 Calheta. 



The Baron Paiva records the occurrence of the H. arcta on 

 the Southern Deserta ; but whether this habitat may be trusted 

 I have no means of deciding. The Bugio, however, is not at all 

 an improbable locality for the species. 



( Rimula, Lowe.) 



Helix arcinella. 



Helix fausta, /3. et 7., Lowe, Prim. ; Append, xiv. (1851) 

 arcinella, Id., Proc. Zool. Soc. Lond. 181 (1854) 

 Paiva, Mon. Moll. Mad. 35 (1867) 



Habitat Maderam, semifossilis ; in stratu conchy lifero juxta 

 Canical, sat vulgaris. 



This little Helix, which was regarded originally by Mr. 

 Lowe as merely a small state ( the ' var. y. minima ') of his H. 

 fausta, has been observed hitherto only in a subfossil condition 

 at Canial, where it is tolerably common. In general size and 

 proportions it has much the prima facie aspect of the smaller 

 examples of the //. arcta ; nevertheless it may be known readily 



