MADEIRAN GROUP. 109 



Sanctum ; et recens et semifossilis. In Portii Sancto ipsissimo 

 semifossilis solum occurrit. 



Although unmistakeably aboriginal, the H. subplicata be- 

 longs to the same subgeneric type as the common European H. 

 aspersa ; and next to the H. Lowei, Fer., it is the largest of 

 the Helices of the Madeiran archipelago. It is peculiar to Porto 

 Santo and the small adjacent islet known as the Ilheo de Baixo, 

 which latter indeed may be regarded as its present head-quar- 

 ters ; for although it is tolerably common in a subfossil condi- 

 tion in many of the calcareous deposits of the former (as, for 

 instance, at the Zimbral d'Areia, and on the Campo de Baixo), 

 it is only on the Ilheo de Baixo that it has hitherto been ob- 

 served in a recent (as well as subfossil) state, it having been 

 first detected there, alive, by myself and the late Kev. W. J. 

 Armitage, in the spring of 1848 (up to which date it had been 

 universally looked upon, though it was not so recorded by 

 PfeifFer, as extinct). J 



The H. subplicata is perhaps, on the average, a trifle larger 

 than the common If. aspersa, Miill., with its spire more ele- 

 vated, its suture more impressed, and its whole contour more 

 globose ; but it is par excellence remarkable for its uniformly 

 pale olivaceous- or yellowish-brown surface, which is quite de- 

 void of markings or bands, and for the very coarse and rather 

 irregular oblique curved plicae with which it is roughened, the 

 nucleus alone (which is usually decorticated, and more or less 

 plumbeous) being comparatively free from sculpture. There is 

 no trace of an umbilicus, or perforation ; the shell is thin, and 

 opake (though brightly polished, and somewhat opaline, within 

 the large subcircular aperture ) ; there are more or less decided 

 indications of coarse granules on and between the ribs ; and the 

 basal whorl is broad and inflated, with the peristome acute and 

 but very slightly recurved. 



( Helicomela, Lowe.) 



Helix Bowdichiana. 



Helix Bowdichiana, Fer., Hist. i. 225. t. 28 B. f. 5, 6 

 punctulata, 7, Pfeif., Mon. Hel. i. 194 (1848) 

 Vargasiana, Id., Proc. Zool. Soc. Lond. 109 (1848) 

 Bowdichiana, Lowe, Proc. Zool. Soc. Lond. 172 



(1854) 

 Alb., Mai. Mad. 83. t. 17. f. 16, 17 



(1854) 

 Paiva, Mon. Moll. Mad. 73 (1867) 



1 Sowerby's original diagnosis of the species was consequently drawn-up 

 from a subfossilized, and almost colourless, example. 



