104 TE8TACEA ATLANTICA. 



Helix membranaoea, Alb., Mai. Mad. 47. t. 12. f. 8-10 



(1854) 

 „ „ Pawa, Mon. Moll. Mad. 11 (1867) 



Habitat Maderam ; in sylvaticis mtermediis umbrosis, nec- 

 non sub folus arborum emortuis, degens, sed nunquam vulgaris. 

 In statu semifossili ad Canical Eev. R. T. Lowe parcissime 

 collegit. 



The H. membramacea, which is widely, though not very 

 abundantly, scattered over the wooded districts, particularly in 

 the damp shady ravines, of Madeira proper, maybe known by its 

 extremely thm, flexible, pellucid, Vitrina-like substance, by the 

 paucity of its volutions (which vary from about 4 to 4^-) and the 

 largeness of its aperture, and by its pale yellowish- or even green- 

 ish-corneous hue, which has often an obsolete rosy additional 

 ti n o-e, — as though to affiliate the species with the closely-allied 

 H. erubescens. Its basal whorl is rather distinctly keeled, the 

 keel however becoming evanescent at the aperture (the margins 

 of which are simple and acute, with the upper one not at all 

 deflexed); its umbilicus is altogether absent ; and its entire sur- 

 face is malleated and lightly transverse-plicate, as well as 

 freckled all over with yellowish-white, subopaque, irregular 

 specks and broken-up, elongate, more or less confluent milky 

 markings — which are usually condensed about the keel into 

 something approaching to a narrow but disjointed fascia. 



The Baron Paiva records this Helix as occurring also on a 

 little uninhabited rock off the north of Porto Santo, known as 

 the ' Ilheo da Fonte d'Areia ; ' but the species is so eminently 

 characteristic of the damp sylvan districts, at a rather high alti- 

 tude, in Madeira proper that I cannot but suspect that some error 

 must have arisen concerning the former habitat (and more par- 

 ticularly so, since the Baron's material was not collected by him- 

 self). I think therefore that further evidence is required before 

 the H. membranacea can safely be cited as Porto-Santan, or 

 even indeed as extra-Madeiran. 



Helix farva. 



Helix furva, Lowe, Cambr. Phil. 8. Trans, iv. 40. t. 5. f. 2. 

 (1831) 

 „ „ Pfeiff., Mon. Eel. i. 29 (1848) 

 „ „ Lowe, Proc. Zool. Soc. Land. 165 (1854) 

 „ „ AW., Mai. Mad. 48. t. 12. f. 17-19 (1854) 

 „ „ Paiva, Mon. Moll. Mad. 12 (1867) 

 Habitat Maderam; in excelsioribus (vel graminosis vel syl- 

 vaticis) occurrens. In statu semifossili ad Canical rarissime 

 invenitur. 



