128 



of myself, on every rock and island of the group, have, 

 it appears, so nearly exhausted the whole number of 

 species which lately remained to be founds that the con- 

 chological statistics are perhaps^ at the present time, 

 more accurate than those of any other department of the 

 fauna: and, independently of the modifications which 

 have been manifestly brought about, in some few instances, 

 by isolation, siace the periods of subsidence, it is truly 

 singular to remark how every detached portion of the 

 entire cluster harbours real species, which are now pecu- 

 liarly its own. Thus (to select an illustration from 

 amongst the most anomalous of the endemic forms), we 

 have in Madeira proper, Porto Santo, and on the South- 

 em Dezerta, respectively, true representatives, in the 

 Helix tiarella, coronata, and coronula, — which in all 

 probability stiU. occupy the positions (or nearly so) of 

 their original debut upon this earth. Considering the 

 sluggish, or sedentary, nature of the Terrestrial Mollusks, 

 it is extremely likely (nay, almost certain) that many 

 intermediate links, radiating from the same type, were 

 lost for ever, when the gigantic movements which rent 

 this ancient region were in course of operation : so that, 

 if such were in reahty the case, we need not be surprised 

 that one at least of this small geographical nucleus should 

 have been preserved on three of the existing islands of 

 the group. That these are actual species (saved alive 

 from their fellows, after the wholesale destructions ia 

 this Atlantic province had been completed), and no 

 results of insular development, is demonstrated by the 



