MADEIRAN GROUP. 215 



darker bands more frequently developed ; and its aperture is 

 proportionately a trifle wider, or not so narrowly and obliquely 

 produced. It has likewise a remarkable tendency to have its 

 apex white and decorticated, sometimes to such an extent that 

 the nucleus becomes abortive and partially destroyed, under 

 which circumstances the shell has naturally a more tumid or 

 ventricose appearance. Like many of the Pupce it seems to 

 have a larger and a smaller state, the representatives of the 

 latter being generally more acute at their extremity than those 

 of the former. 



The P. vincta, which is confined to damp spots in Madeira 

 proper, appears, like the P. cheilogona, to be found more parti- 

 cularly in the north of the island. Yet its habits are not the same 

 as those of that species ; for, whilst the cheilogona is to be met 

 with, almost invariably, adhering to the fronds of ferns at a 

 high elevation, the vincta, on the contrary, infests the dripping 

 masses of Marchantia polymorpha which pad the rocks at a 

 low altitude. Indeed, so far as my own experience is concerned, 

 it may be said to occur especially on the level of the shore ; 

 though in all probability it will be found to ascend to a certain 

 slight elevation. It was obtained in great profusion by Mr. 

 Lowe and myself, during June 1850 and August 1855, at the 

 edges of the first waterfall from Sao Vicente, along the beach 

 road to Seisal ; and Mr. Lowe captured it in a similar situation 

 at the Passa d'Areia, on the other (or eastern) side of the Sao 

 Vicente ravine. Several boxes of it have also been communi- 

 cated by the Baron Paiva (containing generally a large admix- 

 ture of the P. Loweana, Woll., regarded erroneously by him as 

 P. concinna, Lowe), and which / believe were obtained from 

 the lower regions of the Ribeira do Inferno, and those of the 

 Boa Ventura. 



Pupa irrigua. 



Pupa irrigua, Lowe, Ann. Nat Hist. ix. (1852) 

 Id., Proc. Zool. Soc. Lond. 208 (1854) 

 Alb., Mai. Mad. 63. t. 15. f. 27/28 (1854) 

 Paiva, Mon. Moll. Mad. 124 (1867) 



Habitat Maderam, prsecipue australem ; inter gramina (Des- 

 champsia argentea, Lowe) ad rupes irriguas aquosas, hinc inde 

 vulgaris. 



Like the last two species, the P. irrigua is rather a large 

 Pupa; but it is more strictly oblong (or less widened poste- 

 riorly, and therefore less ovate) than either of them. Its volu- 

 tions are somewhat flattened, and therefore the suture is not 

 greatly impressed ; in colour it is of a pale yellowish, or olive- 

 brown (occasionally with indistinct bands) ; and its spire 



