a 



; 



:^ 



\ 



Ch. XLL] 



REFERENCE TO THE ORIGIN OF SPECIES, 



423 



At tlie time of my visit in 1854 tlie known living species 

 Madeira proper, excluding the 



modern intruders above 



amounted 



only 12 of the whole heing common 



both islands ; and. 



what is of no small significance, even some of these 12 

 beino- represented in the two islands by distinct varieties. 



re that of two of the 



mor 



In truth, the discordance is 



six great zoological provinces of the globe before described, 



same 



If we then refer to the fossil groups, w^e find 36 species in 



Madeira 



common 



the two islands, and 5 of these 8 being represented by 

 distinct varieties in each island respectively. It was to be 

 expected that as Porto Santo is much less cultivated than 

 Madeira, and has only a small human population, the fossil and 



much more 



Madeir 



us 



to reject as spurious or as modern interlopers those 



missin 



fossil group of that island. These fossils occur at Cani9al 

 near the eastern extremity of Madeira,^ in prodigious 

 numbers, imbedded in a superficial deposit of calcareous 



sand and mud. Amon 

 uous species of 



! most common is a conspic- 

 form named Helix delphinula 



Tom 



its resemblance to the marine genus Delphinula), 



from 



Another smaller but very characteristic 



Helix tia- 



must 



swarmed in the Newer 

 became so extremely rare 



that for a Ion 



time it was supposed to be extinct, until a few surviv- 

 ing individuals were detected by Mr. WoUaston, in 1855, 

 at a great height on some precipitous and nearly inac- 

 cessible rocks in the interior of Madeira. Two species of 

 Achatina and two of Pupa, also fossil at Canical, are supposed 



have disappeared from the 

 small dimensions they may 



become 



* See Map, fig. 137, p. 405. 



