98 TESTACEA ATLANT1CA. 



( Tberus, Monf.) 



Helix Wollastoni. 



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

 Pfeiff., Mon Hel. iii. 169 (1853) 



Lowe, Proc. Zool. Soc. Lond. 198 (1854) 



Alb., Mai Mad. 22 [nee ? ff] (1854) 



Paiva, Mon. Moll. Mad. 100 (1867) 



Habitat Portum Sanctum ; in monte orientali ' Pico do 

 Concelho,' sub lapidibus vulgaris. Semifossilis ad, necnon 

 juxta, Zimbral d'Areia prsecipue invenitur. 



Peculiar to Porto Santo, where it was first detected (in a 

 recent state) by myself, during April of 1849, on the slopes of 

 the Pico do Concelho, in the east of that island, having, how- 

 ever, been found in a subfossil condition by Mr. Lowe so far 

 back as in 1828. It swarms, beneath stones, on that particular 

 mountain, but I have never met with it elsewhere ; and even in a 

 subfossil state it is only at the Zimbral d'Areia (which abuts on 

 the base of the Pico do Concelho), and in its vicinity (as, for 

 instance, in the muddy deposits of a sea-cliff below the Pico 

 dos Macaricos) , that it has hitherto, so far as I am aware, been 

 brought to light. 1 



The H. Wollastoni may be known by its acutely carinated 

 basal volution, and minutely granulose, obliquely plicate 

 surface, the plicae being more or less undulate, irregular, 

 and here and there confluent. In colour it is usually of an 

 olivaceous- or yellowish-brown, and with two very obscure 

 darker bands on each whorl, generally so obscure as to be 

 barely traceable, but often appreciably developed ; and the 

 under-part of the ultimate volution is either altogether con- 

 colorous, or else ornamented with a narrow darker fascia at a 

 little distance from the keel. 



The present Helix belongs to the same type as the subfossil 

 Canarian H. digna, Mouss., from Gomera, and (more especially) 

 as the Sicilian H. scabriuscula, Desh. (Encycl. Meth. ii. 130), 

 with which latter indeed it has a great deal in common. It is, 

 however, smaller and rather less flattened than the scabriuscula 

 (its spire being more exserted), its oblique transverse rugce are 

 more elevated or developed, its keel (which is less compressed) 



account of the unfortunately selected one which was previously imposed upon 

 it by Sowerby, I have thought it sufficient merely to call attention to the 

 fact, leaving the alteration in the hands of those who may regard it as 

 necessary. 



1 In the Baron Paiva's Monograph an albino state of the H. Wollastoni is 

 mentioned as occurring on the Pico Branco ; but I feel it exceedingly pro- 

 bable that that habitat was inserted through a lapnuz calami, or by mistake. 



