We must not however omit to notice, that some few of these endemic _Helices_ appear to have been gifted (as we should _a priori_ anticipate) with more rapid capabilities for diffusion than the rest. Thus, the _H. erubescens_ and _paupercula_ seem not only to have colonized the entire province of which the Madeiras are detached fragments, but to have even found their way to that distant portion of it which now constitutes the Azores. The _H. polymorpha_ has also penetrated the Madeiran region throughout; and being, like the _H. erubescens_, peculiarly sensitive to the action of external influences, we perceive, in consequence, that almost every island and rock has now its own especial phasis of it. So greatly indeed is that species beneath the control of local circumstances, that the very districts of an island as insignificant as Porto Santo have each their separate races to boast of. On the Pico d'Anna Ferreira it assumes a form to which the name of _H. attrita_ has been applied; when on the Ilheo de Baixo, it is the _H. papilio_; at the Zimbra d'Areia, on the Pico de Conseilho, and in the Ribeira da Coxinha, it is the _H. pulvinata_; and, in many other situations widely removed _inter se_, it puts on the shape (variable, both in size and hue) to which the title of _H. discina_ has been given. But, if we leave Porto Santo, and follow this Protean _Helix_ into the other divisions of the group; we meet with it on the Dezertas as the _H. senilis_ (those moreover from the central island having a much more open umbilicus than is the case in the northern and southern ones), whilst in Madeira proper it constitutes the _H. lincta_ (with an additional pale variety for the calcareous district of Canical),--and the _H. saccharata_, from the Sao Lourenco promontory.