232 TEST ACE A ATLANTIC A. 



deira proper, to the P. sphinctostoma, it seems impossible not 

 to acknowledge them as truly and specifically distinct. 



Judging therefore from the material now before me, the P. 

 degenerata may be said to differ from its immediate allies, and 

 more particularly from the P. monticola, in being less strictly 

 cylindrical (it having a decided, though not very conspicuous, 

 tendency to be slightly and gradually attenuated towards the 

 apex), in its volutions (which are exceedingly tumid) having 

 their costae very coarse, remote, and oblique, and in its aperture 

 being extremely small and rounded, with the plaits so unusually 

 diminished in size as to be almost obsolete. Indeed even the 

 outer ventral one is very short and small ; whilst the only other 

 three which are traceable (namely the inner ventral one, the 

 lower one on the columella, and the middle palatial one) are 

 greatly reduced, inconspicuous, and deeply immersed. 



Pupa monticola. 



Helix monticola, Lowe, Cambr. Phil. S. Trans, iv. 63. t. 6. 

 f. 33 (1831) 



Pupa monticola, Pfeiff., Mon. Eel. ii. 335 (1848) 

 Lowe, Proc. Zool. Soc. Lond. 212 (1854) 



Alb., Mai. Mad. 67. t. 16. f. 3, 4 (1854) 



Paiva, Mon. Moll. Mad. 133 (1867) 



Habitat Portum Sanctum ; status typicus prsecipue in cacu- 

 minibus montium, sed ' var. /3. pumilio ' in rupium fissuris in 

 locis minus elevatis plerumque congregat. 



This little costate Pupa is locally abundant in the fissures, 

 and on the ledges, of the rocks in Porto Santo, to which island 

 it seems to be peculiar, occurring both amongst small stones 

 and vegetable detritus at a high elevation (like the P. calathis- 

 cus), and likewise in exposed spots of a comparatively low alti- 

 tude. In the former case it is, on the average, a trifle larger 

 and paler, with the ultimate volution just appreciably more 

 developed, the costse a little more flexuose and remote, and the 

 upper palatial plait not quite so strongly expressed ; and as this 

 is the particular state which was originally described by Mr. 

 Lowe, it must perhaps be regarded as the normal one. Under 

 this phasis the species occurs sparingly, often in company with 

 the P. calathiscus, on the summits of the Pico de Facho, the 

 Pico Branco, &c. Nevertheless, so far as my own observations 

 are concerned, it is far more abundant in certain exposed, wea- 

 ther-beaten spots but slightly raised above the sea-level ; and in 

 such situations the shell is usually a trifle smaller, darker, and 

 more solid, with its costse a little less sinuate and more closely 

 set together, and with its ultimate volution and aperture just 



