126 TESTACEA ATLANTICA. 



much depressed, or sunken, as to seem well-nigh concave] , no 

 less than in their few and rapidly-increasing volutions, and 

 their singular habit of coating themselves over with an envelope 

 of hardened mud, the two species have undoubtedly a vast deal 

 in common. And yet they are completely, and utterly, distinct. 

 Apart from the thinness and flexibility of its composition, the 

 H. latens differs from the excessively solid and robust H. ob- 

 tecta in being smaller and (when denuded of its muddy covering) 

 of a more or less olivaceous or greenish-brown tinge, in its um- 

 bilicus being relatively a little narrower and less spiral, and in 

 its having a volution less. 1 



In its mode of life the H. latens may be described as the 

 exact opposite of the H. obtecta ; for while the latter occurs in 

 the driest, sunniest, and most calcareous spots which even the 

 barren and exposed island of Porto Santo can furnish, the 

 present species is confined to the damp sylvan districts of 

 Madeira proper at intermediate and lofty elevations, where it 

 is usually to be met with amongst loose rubble, and coarse 

 vegetable detritus, on the ledges, and at the base of, the per- 

 pendicular rocks which form so marked a feature throughout 

 the wooded ravines. I first detected it, about thirty years ago, 

 in the Ribeira de Sta. Luzia, above Funchal ; and it has since 

 been obtained by Mr. Leacock, Mr. Lowe, Mr. Watson, Senhor 

 Moniz, the Baron Paiva, myself, and others, in somewhat 

 similar spots, in various parts of the island. 



Helix paupercula. 



Helix paupercula, Lowe, Cambr. Phil. S. Trans, iv. 47. t. 5. 



f. 19 (1831) 



Pfei/., Mon. Hel. i. 189 (1848) 



Lowe, Proc. Zool. Soc. Lond. 175 (1854) 



Alb., Mai. Mad. 35. t. 8. f. 27-30 (1854) 



Mouss., Schw. Denksch. xv. 135 (1857) 



Paiva, Mon. Moll. Mad. 61 (1867) 



Mouss., Faun. Mai. des Can. 60 (1872) 



Watson, Journ. de Conch. 222 (1876) 



Habitat ins. omnes Maderenses [sc. Maderam, Portum 

 Sanctum, et tres Desertas] ; in aridis apricis inferioribus sub- 

 maritimis, hinc inde vulgatissima. Semifossilis in Poitu 



1 Pfeiffer was certainly mistaken in describing the H. latens as pilose. 

 There is no trace of pilosity in any of the numerous specimens which I have 

 ever examined ; and indeed even if there had been, until the shells were 

 thoroughly cleaned (a most difficult operation with subjects so unusually 

 fragile and flexible), it would have been completely concealed from view. As 

 in most of these immediately allied forms, the surface is minutely and very 

 delicately (but perhaps somewhat unevenly) granulated. 



