MADEIRAN GROUP. 167 



searches throughout the entire Group of islands, has con- 

 tributed so much to our store of knowledge, not merely of the 

 Land-Mollusca but in many other departments of Natural 

 Science. 



Helix oxytropis. 



Helix oxytropis, Lowe, Cambr. Phil. S. Trans, iv. 57. t. 6. 



f. 18 (1831) 



Pfeiff** Man. Hel. i. 190 (1848) 



Lowe, Proc. Zool. Soc. Loud. 186 (1854) 



Alb., Mai. Mad. 37. t. 9. f. 8-10 (1854) 

 Paiva, Mon. Moll. Mad. 46 (1867) 



Habitat Portum Sanctum; sub lapidibus in intermediis 

 degens. Semifossilis rariss. ; sed in statu majore (= /?. sub- 

 carinulata, mihi) paulo magis copiose reperitur. 



As already stated, the H. oxytropis belongs to the same 

 geographical type as the six preceding species ; yet it is 

 thoroughly distinct from them all, never merging into any of 

 them, so far as I am aware, by even doubtful aberrations. 

 Although exceedingly similar in colouring (which is unmis- 

 takeably characteristic), and a good deal so in form and sculp- 

 ture, to its allies, it has the volutions (the basal one of which is 

 sharply and singly keeled) conspicuously more flattened, 

 causing the upper portion of the shell to be more strictly 

 conical or roof-shaped (though apically somewhat rounded and 

 obtuse). Its granulations, although coarse, are relatively much 

 less developed than those of the H. echinoderma, echinulata, 

 bicarinata, and vermetiformis, but rather more so than is the 

 case in the H. LeacocJdana and turricula. 



The H. oxytropis, which is equally confined to Porto Santo 

 with its immediate allies, is less abundant than the echinulata 

 and bicarinata. Nevertheless it is common locally, occurring 

 beneath stones on the mountain-slopes ; and so far as my own 

 observations are concerned, it is more prevalent in the south- 

 eastern extremity of the island than elsewhere, particularly on 

 the two closely adjoining peaks opposite to the Ilheo de Cima, 

 known as the Pico de Baixo and the Pico dos Maparicos. 



In a subfossil condition the H. oxytropis is found very 

 sparingly; indeed, so far as I have myself observed, I should 

 say that it was decidedly rare. There is, however, a larger 

 phasis of the shell with the spire relatively more elevated and 

 apically-acute, and with the volutions very obsoletely keeled in 

 the centre which I have taken on various occasions more 

 abundantly. Under this form, the shell has much the size and 

 prima facie aspect of certain states of the H. cheiranthicola ; 

 though, on a closer inspection, its more densely granulated 



