HELIX. 



H. MEMBRANACEA Lowe, 1852. PI. ">1, figs. 4", 46. 



Impcrforatc, depressed globose, excessively thin, flexible, pellucid, 

 yellowish or greenish corneous, usually more or less variegated with 

 opaque whitish flecks and reticulations, which sometimes form ;i 

 stripe at the central keel; whorls 4, rapidly increasing; spire low, 

 obtuse; body-whorl acutely carinalcd at the middle, the carina be- 

 coming obsolete toward the aperture ; not deflected anteriorly ; aper- 

 ture large, broad oval lunar, oblique; peristome simple, thin, end- 

 scarcely converging; columella simple, arcuate. 



Diam. 10, alt. 6 mill. 



Madeira. 



The excessively thin, easily indented substance of this species will 

 distinguish it from any of its allies. The last whorl is not so acute- 



o / 



ly carinated as in H. webbiana. 



H. CUTICULA Shuttleworth. PI. 51, figs. 47-49. 



Irnperforate, depressed-conic, very thin and fragile, with a silky 

 lustre, light green, costulate-striate ; spire low, conic, apex prom- 

 inent; suture impressed ; whorls '!, rapidly increasing, convex below 

 the sutures and on base, but concave above and below the prominent 

 peripheral carina; body-whorl large, depressed, carinated to the 

 aperture, not deflected anteriorly, indented at the axis ; aperture 

 transversely oval, angulate at position of carina ; peristome acute, 

 membranous; columella deeply, vertically entering. 



Diam. 7, alt. 4' mill. 



Tencriffi' and PU/IIHI, (Wym/'/Y.--. 



Section VIII. IUERUS Montfort, 1810. 



Helices of the section I her us are very numerous, both in species 

 and individuals in central and southern Italy, and in Sicily ; and 

 curiously enough, there have been a few trans-Mediterranean spe- 

 cies discovered in recent years. Then- is great lattitude of opinion 

 concerning the synonymy of the group, arising from the fact that 

 transition forms between many of the " species " render any hard- 

 and-fast lines of demarkation between them wholly arbitrary; and 

 the subject has been still further complicated by a number of diag- 

 noses of" new species," without figures, each of which admits of be- 

 ing applied to several forms. 



The Sicilian species form a perfect series of gradations between 

 the carinate flattened forms and the globose elevated ones. They 



