144 TEST ACE A ATLANTIC A. 



what apt to be confounded with each other, I have thought it 

 desirable to give an emended diagnosis of them both. The H. 

 fausta is more globose ( and, on the average, somewhat smaller) 

 than the obserata, as well as less keeled, its spire (although ob- 

 tuse) being more elevated ; its aperture is a trifle less narrowed 

 and horizontal, the columella being just perceptibly longer ; and 

 its surface is not only more hispid or pubescent (the H. obse- 

 rata being practically bald), but marked with very much finer 

 and more obsolete lines. It is also a little less solid in sub- 

 stance, and appreciably more opaque. 



There is, however, a state of the shell, which I have enun- 

 ciated as the ' var. ft. robustaj which is distinctly larger and a 

 little more keeled, or less globose, thus making an approach 

 towards the ff. obserata ; nevertheless it is quite as thickly pu- 

 bescent as the typical one, and its sculpture is quite as fine. 



In size, outline, and colouring, the H. fausta has much the 

 general appearance (at all events in its normal condition) of the 

 H. capsella. But it is a trifle larger than that species, and 

 more globose (being convexer both above and below), it pos- 

 sesses half a volution more, its perforation is altogether closed 

 over, instead of but partially so), its aperture is narrower and 

 more depressed, and there are more evident traces of a corneous 

 thickening, shaping out an obsolete tooth, within the lower 

 margin of the peristome. 



The H. fausta occurs only in Madeira proper, where it is 

 one of the rarest of the Helices. It was first detected, during 

 October of 1829, by Mr. Lowe, who found a single example of it 

 under the dead leaves of a Sempervivum, on a dry rock, in the 

 chestnut-woods of the Boa Ventura (about two miles up the 

 ravine from the sea), on the western side of the Ribeira. For 

 twenty-six years this specimen remained unique ; but in the 

 summer of 1855 the species was again met with, though very 

 sparingly, by Mr. Lowe and myself, in the same spot in the Boa 

 Ventura in which he took his original type; and we also ob- 

 tained a few examples of it in the Ribeira de Sao Jorge, as well 

 as at the Passa d'Areia near Sao Vicente, and others (still fur- 

 ther to the westward) between the Ribeira da Janella and Porto 

 Moniz. The Baron Paiva records its occurrence, likewise, in 

 the Ribeira Funda, near Seissal. 



In a subfossil condition, the H. fausta is tolerably common 

 near Canical. 



Helix obserata. 



T. imperforata, orbiculato-discoidea, lenticularis, distincte 

 carinata, subtus inflato-convexa, solidiuscula, subnitida, fere 

 (vel omnino) calva, utrinque grosse obtuse et subflexuose plica- 



