produced by great Geographical Changes. 387 



Section 5. — The preservation, at the p'esentday, of isolated rem- 

 nants of the Secondary Continents, and of the Secondary Fauna 

 inhabiting them. 



I have endeavoured to show that a remnant of the continental 

 tracts of the secondary period appears in the present Australian 

 continent. Now it is an important fact that, with the possible 

 exception of the Stereognathus, the nearest living affinities of the 

 Mammalia yet discovered in secondary formations exist in Aus- 

 tralia and its adjacent islands*, and in Madagascar. Many of 

 the trifid footprints from the red sandstone of the Connecticut 

 valley are admitted to be those of birds ; and Sir Charles Lyell 

 statesf that in the impressions of the skin in some of them, 

 Prof. Owen has recognized a resemblance to the skin of existing 

 Struthionidse. We cannot any longer, I think, hesitate to admit, 

 notwithstanding the absence of osseous remains, that birds having 

 affinities with the modern Struthionidse and Dinornidse existed in 

 the triassic period. It is therefore significant to find that these 

 modern Struthionidse exist only (with the exception of Sumatra) 

 in lands which, I have attempted to show, are remnants of the 

 secondary continents ; and that as regards all the other modern 

 wingless birds except the Struthionidse, i. e. the birds of Mada- 

 gascar, the Mauritius and adjoining islands, and of New Zealand, 

 they exist only in isolated remnants of those continents : and not 

 less significant is it, that these forms of Mammalia and of modern 

 wingless birds are associated with vegetable forms having the near- 

 est affinities to the vegetation of the secondary and carboniferous 

 periods — as witness the tree ferns and Cycadse of Madagascar, 

 Australia, and New Zealand, and the Araucarise of various parts 

 of the southern hemisphere ; wmile in the Cestracion and Trigonia 

 of the Australian shores are preserved the only living examples 

 of those secondary genera. 



Chelonia, only the last three appear to have survived the post-creta- 

 ceous changes ; the other existing orders, Amphibia, Batrachia, and 

 Ophidia, may, however, be expected to occur in the cretaceous formations. 

 Of the cretaceous fish, not only did all the orders survive these changes, 

 but the suborders and families also, and even about a fourth of the genera ; 

 while of the Mollusca, about a third of the genera (including the Cephalo- 

 poda) only perished. 



* Not merely Tasmania, but New Guinea and Arroo, which have been 

 shown by Mr. Wallace to possess a fauna entirely agreeing with Australia, 

 and differing as entirely from the islands of the Indian Archipelago near to 

 them. These two last-named islands appear to have been very recently 

 severed from the ancient continent of Australia by the oscillations pro- 

 duced by the intensely active volcanic band of the Indian Archipelago. 



t Man. Elem. Geol. 1851, p. 298. 



2D2 



