Jan. 1834. fossil remains. 209 



not being perforated for the vertebral artery, indicates its 

 affinity : some other parts, however, of its structure, pro- 

 bably are anomalous. 



The most important result of this discovery, is the con- 

 firmation of the law that existing animals have a close 

 relation in form with extinct species. As the guanaco is the 

 characteristic quadruped of Patagonia, and the vicuna of the 

 snow-clad summits of the Cordillera, so in bygone days, 

 this gigantic species of the same family must have been con- 

 spicuous on the southern plains. We see this same relation 

 of type between the existing and fossil Ctenomys, between 

 the capybara (but less plainly, as shown by Mr. Owen) and 

 the gigantic Toxodon; and lastly, between the living and 

 extinct Edentata. At the present day, in South America, 

 there exist probably nineteen species of this order, dis- 

 tributed into several genera ; while throughout the rest of 

 the world there are but five. If, then, there is a relation 

 between the living and the dead, we should expect that the 

 Edentata would be numerous in the fossil state. I need 

 only reply by enumerating the megatherium, and the three 

 or four other great species, discovered at Bahia Blanca; 

 the remains of some of which are also abundant over the whole 

 immense territory of La Plata. I have already pointed out 

 the singular relation between the armadilloes and their great 

 prototypes, even in a point apparently of so little importance 

 as their external covering. 



The order of rodents at the present day, is most con- 

 spicuous in South America, on account of the vast number* 

 and size of the species, and the multitude of individuals : 

 according to the same law, we should expect to find their 

 representatives in a fossil state. Mr. Owen has shown how 

 far the Toxodon is thus related; and it is moreover not 



* In my collection Mr. Waterhoiise distinguishes twenty-seven species 

 of mice ; to these must be added about thirteen more, known from the 

 works of Azara, and other naturalists ; so that we have forty species, 

 which have actually been described as coming from between the Tropic 

 and Cape Horn. 



VOL. III. P 



