MADEIRAN GROUP. 241 



Can 190, in the south-east of Madeira proper, from beneath the 

 dead leaves of Sempervivum glandulosum, Ait., — which im- 

 plies a modus vivendi resembling - , apparently, that of the C. 

 exigua. The more obtuse, fusiform outline, and greater obesity, 

 of the shell, the whorls of which are slightly diminished in num- 

 ber, and consequently somewhat elongated and enlarged, added 

 to its surface being less opake and its costae both closer and less 

 elevated, give it such a different aspect, when viewed alongside 

 (for instance) the 'status a. raricostcC from Porto Santo, that 

 it is difficult to believe that it can be conspecific with that very 

 solid and powerfully ribbed modification of the G. deltostoma. 

 Yet Mr. Lowe, even whilst publishing it provisionally as new, 

 recorded his doubts as to whether it would prove in reality to be 

 more than ' a mere local forcn or variety of the extremely poly- 

 morphous common Madeiran G. deltostoma, — adding that it 

 approached so nearly to his ' status h. depauperata ' of that 

 species that it seemed to be almost connected (through the 

 latter) with the ordinary type. And indeed there can be little 

 doubt, I think, that it is connected, — the ' 8. depauperata ' 

 possessing the same peculiarity of volutions, surface, and sculp- 

 ture, as the ohesiuscula, from which it mainly differs in its 

 smaller size, its rather less thickened outline, and its more 

 pallid, unspeckled hue. Therefore it seems to me that we 

 must be content, despite its essentially different aspect from 

 the opposite extreme of the species, to regard the ohesiuscula as 

 representing only another, but remarkable, phasis of the mar- 

 vellously plastic G. deltostoma. 



In a subfossil state the G. deltostoma occurs sparingly in 

 Porto Santo (where I have met with it at the Zimbral d'Areia), 

 and on the Southern Deserta ; but I am not aware that it has 

 yet been observed in Madeira proper. 



Clausilia exigua. 



Helix exigua, Lowe, Cambr. Phil. S. Trans, iv. Gfi. t. 6. 

 f. 39 (1831) 



Clausilia exigua, Pfeiff., Man. Jlel. ii. 485 (1848) 



„ „ Lowe, Proc. Zool. Soc. Load. 216 (1854) 



„ „ Alb., Mai. Mad 71. t.16. f. 20-22 (1854) 



„ ,, Paiva, Mon. Moll. Mad. 144 (1867) 



Habitat Maderam ; sub foliis Sempervivi aridis emortuis 

 ad rupes submaritimas crescentibus pi-secipue latitans. 



This little Clausilia has much the outline, fewer volutions, 

 and thinner substance, of the ' status 8. depauperata ' of the 

 last species ; nevertheless it is still smaller and somewhat more 

 apically-obtuse, its whorls are a trifle more convex, its costae are 



R 



