136 TEST ACE A ATLANTIC A. 



Both the H. dealbata and fictilis are solid, depressed, and 

 somewhat turbo-lenticular shells, with a small but distinct 

 umbilicus, and with their peristome continuous, but neither 

 much raised nor much rounded across the body- volution. In 

 its normal state the dealbata is larger, less flattened, and more 

 solid than the fictilis, its sculpture is altogether rougher (the 

 transverse costate lines being coarser and the granules more 

 numerous), and its surface has usually a whitened and bleached 

 appearance, — with only a faint trace (sometimes indeed none at 

 all) of an infra-cariual band, but with the aperture within, and 

 the peristome, more or less obscurely ochreous. In certain 

 examples, however, which can hardly be treated as representing 

 a definite ' variety,' the colour is darker, being of a slightly 

 yellowish- or plumbeous-brown ; and in others the granulations 

 are both fewer in number and well-nigh obsolete. 



From the H. onicromphala the dealbata may be known by 

 being larger, paler, more solid, and more depressed, by its sur- 

 face being more coarsely costate-striate but less roughly (and 

 less thickly) granulated, by its umbilicus being relatively a 

 trifle wider, by its basal volution being less suddenly deflected 

 in front, and by its aperture (which is more developed) being 

 ochreous internally. 



The H. dealbata is most abundant in dry calcareous places 

 in Porto Santo ; and on the adjacent islet of the Ilheo de 

 Baixo it absolutely swarms ; but I am not aware that it has 

 been observed in a strictly subfossil state. 



Helix fictilis. 



Helix fictilis, Lowe, Ann. Nat. Hist. ix. (1852) 

 „ „ Pfeif., Mon. Hel. iii. 154 (1853) 



„ „ Loive, Proc. Zool. 8oc. Lond. 196 (1854) 



„ „ Alb., Mai. Mad. 31. t. 7. f. 17-24 (1854) 



„ „ Paiva, Mo7i. Moll. Mad. 55 (1867) 



Habitat Portum Sanctum (insulasque parvas adjacentes) ; 

 hinc inde congregans. In statu semifossili invenitur, sed 

 multo rarius. 



As already implied, the H. fictilis, which is abundant in 

 many districts of Porto Santo, and which occurs also (thougli 

 much more rarely) in a subfossil condition, is typically a 

 smaller and a flatter shell than the dealbata, its spire being 

 more depressed ; and it is also rather less solid and robust, not 

 quite so coarsely striated, and with only a few scattered 

 granules on each volution towards the suture ; and its ultimate 

 and penultimate whorls are more angidated, or less rounded 

 and inflated. The colour, too, is not quite the same, — those 



