131 



Nor does this primaeval excess of its aboriginal beiags 

 strike us more forcibly than does the utter quiescence 

 (if I may so express it) which has been going on amongst 

 them since the remote era of their birth. Although a 

 few have apparently died out* since that epoch, conse- 

 quent perhaps on the change of level and diminished 

 range which took place during the process of subsidence ; 

 we are amazed to find that certaia species which are now 

 limited to particular spots (even whilst unopposed by 

 physical barriers) have been absolutely pecuhar to them 



* Assuming the Helix Lowei and Bowdichiana to be gigantic 

 phases of the H. Portosanctana and punctulata, respectively; four 

 only, namely H. fluctuosa and lapicida, AcJiatina Eulina, and Cyclo- 

 stoma lucidum (the first three of which are extinct throughout the 

 entire group), seem to have altogether disappeared. Nevertheless, 

 the gradual dying-out, as it were, of species, both here and in 

 Madeira proper, is singularly evident. Thus, in the latter, the Cani- 

 9al beds show the H. tiarella to have been once most abundant (it 

 literally teems in those calcareous formations). Yet so rare is it in 

 a recent state, that, until the summer of 1855, when it was detected 

 by myself and the Rev. R. T. Lowe in two remote spots along the 

 perpendicular cliiFs of the northern coast, it was supposed to have 

 been lost for ages. And the same may be said of its counterpart, 

 the H. coronata, in Porto Santo, — which, likewise, swarms in every 

 fossil-bed of that island; but which was, also, until I met with it, 

 on the 15th of December 1848, adhering to slabs of stone at a con- 

 siderable depth beneath the ground, on the extreme eastern peak 

 (opposite to the Ilheo de Cima), imagined to have long passed 

 away. And so, reasoning from analogy, I think it far from impro- 

 bable that the third representative of this little geographical assem- 

 blage, — the H. coronula of the Bugio (which has hitherto only 

 occurred in the mud deposits on the summit of that rock), — may be 

 still alive, though perhaps in very small numbers, on some of the 

 inaccessible ridges of those dangerous heights. 



