128 TESTACEA ATLANTICA. 



it is perfectly true that (like the H. pisana and lenticula) it 

 often exists in a living state on the selfsame ground where its 

 subfossil representatives are to be met with, and that therefore 

 occasional bleached examples might well be mistaken at first 

 sight for subfossilized ones, nevertheless out of all the shells 

 which I have myself ever obtained in a decidedly subfossil con- 

 dition there is certainly none which is less equivocal than the 

 H. paupercula. Although unquestionably scarce about Canical, 

 at the Zimbral d'Areia in Porto Santo I have gathered it in 

 absolute profusion, along with the numerous other species of 

 that prolific locality, and quite as much thickened and super- 

 ficially decomposed as any of them. 



Like the H. obtecta and latens, this insignificant but solid 

 little Helix (which measures only about 2J lines across its 

 broadest part) has the habit of covering itself over with a 

 coating of hardly-cemented earth ; but when the outer envelope 

 has been removed it will be seen to be of either a reddish brown 

 or else of a pale cinereous-grey, with the surface opake and most 

 minutely and densely granulated all over, and with the trans- 

 verse lines of growth tolerably apparent. It is a flattened and 

 planorbiform shell, composed of about 4 whorls, the spire 

 being extremely depressed, indeed often a little concave (though 

 variable in that respect, for sometimes the nucleus is gradually 

 raised and prominent), and the base inflated and convex. Its 

 umbilicus is somewhat large, deep, and spiral ; and its aperture 

 (which is very suddenly, and a good deal, deflected) has a 

 powerful constriction immediately behind it (shaping-out an 

 annular, ridge-like projection), with the peristome thin, almost 

 circular, continuous, and raised. 



( Placentula, Lowe.) 



Helix compar. 



Helix compar, Lowe, Cambr. Phil. S. Trans, iv. 48. t. 5. 



f. 23 (1831) 



Pfei/., Mon. Hel. i. 214 (1848) 



Lowe, Proc. Zool. Soc. Land. 195 (1854) 



Alb., Mai. Mad. 29. t. 7. f. 1-4 (1854) 



Paiva, Mon. Moll. Mad. 50 (1867) 



Habitat Maderam; prsecipue in Pico do Eancho (juxta 

 promontorium Grirao), et circa Camara de Lobos, degens. 



The closely allied Helices of this immediate type, although 

 by no means large, are more or less solid, flattened, and lenti- 

 cular (being slightly convex beneath), with a rather wide and 

 spiral umbilicus, and with a raised, circular, and continuous 

 peristome ; their surface is often strongly sculptured either with 



