408 CHARLES DARWIN 



it is found nowhere else in this quarter of the world. It is 

 now widely distributed; but it may be questioned whether 

 it is in any other place an aboriginal. The bones of a tor- 

 toise at Mauritius, associated with those of the extinct Dodo, 

 have generally been considered as belonging to this tortoise ; 

 if this had been so, undoubtedly it must have been there 

 indigenous; but M. Bibron informs me that he believes that 

 it was distinct, as the species now living there certainly is. 



The Amblyrhynchus, a remarkable genus of lizards, is con- 

 fined to this archipelago; there are two species, resembling 



Amblyrhynchus cristatus. a, Tooth of, natural size, and likewise magnified. 



each other in general form, one being terrestrial and the 

 other aquatic. This latter species (A. cristatus) was first 

 characterized by Mr. Bell, who well foresaw, from its short, 

 broad head, and strong claws of equal length, that its habits 

 of life would turn out very peculiar, and different from those 

 of its nearest ally, the Iguana. It is extremely common on all 

 the islands throughout the group, and lives exclusively on the 

 rocky sea-beaches, being never found, at least I never saw 

 one, even ten yards in-shore. It is a hideous-looking crea- 

 ture, of a dirty black colour, stupid, and sluggish in its move- 

 ments. The usual length of a full-grown one is about a yard, 

 but there are some even four feet long; a large one weighed 

 twenty pounds: on the island of Albemarle they seem to 

 grow to a greater size than elsewhere. Their tails are flat- 

 tened sideways, and all four feet partially webbed. They are 

 occasionally seen some hundred yards from the shore, 

 swimming about; and Captain Collnett, in his Voyage says, 



