364 On the Palwontology of South America, 



at the bottom of some maritime basin, where no animals could 

 exist. 



Posterior to the Triassic system, there commences in Europe 

 a very long period, comprehending the Jura system, in which 

 six formations, at least, often of great extent, succeed, all ex- 

 hibiting distinct faunas ; these are the Lias, the lower Oolite, 

 the great Oolite, the Oxford, Kimmeridge, and Portland 

 deposits. We in vain seek for these extensive formations in 

 America, and with difficulty discover a trace of them in a 

 small isolated locality. The question then very readily occurs, 

 What has been the cause of the non-appearance of the Jura 

 system 1 This, at first announcement, is a startling question. 

 But if, for instance, we suppose that during this long period, 

 the Triassic system, forming perhaps a prolongation of the Bo- 

 livian, and destined subsequently to support the Cretaceous 

 system, was emerged, and formed Continents, we recognise a 

 cause which may explain the want of the Jura system in the 

 New World. It would appear probable, that, during the Jura 

 formation, South America constituted a much larger Conti- 

 nent than at present ; whilst, at the same time, for the expli- 

 cation of existing facts, it is likewise necessary to suppose that, 

 at the conclusion of the Jura deposits, numerous dislocations 

 occurred in America from the sinking and immersion of these 

 same Triassic formations, because they then received the lowest 

 formations of the succeeding epoch. 



The cretaceous formations now appeared on the crust of the 

 globe ; and Nature, after having annihilated the previous fauna, 

 repeopled it with animals, and animal life reappeared on the 

 earth. Whilst, in Europe, numerous Ammonites and other Mol- 

 lusca peopled the ancient seas of the Paris basin and the Medi- 

 terranean, belonging to the Neocomian period, these same seas 

 extended to the northern and western coasts of America, from 

 Columbia to the Straits of Magellan, exhibiting species ap- 

 proximating in form, and even identical in kind. In fact, not 

 only do the Neocomian formations of Columbia afford fifty per 

 cent, of species related in form to those of the Paris basin of 

 this system, but no fewer than twenty per cent, of species quite 

 identical are found simultaneously in Europe and in America. 



