CONCLUSIONS. 415 



been detected. In fig. 389 are figured the jaw and teeth of 

 PalfBotheria, from the tertiary strata of the Isle of Wight. 10 

 is the canine tooth of P. commune, and 1 1 the grinding sur- 

 face of jthe molar tooth of P. medium; 12 is one half of the 

 lower jaw of P. minus, and 13 are the molars of a Dichobune, 

 another extinct genus of the PAL^OTHEEID^. The mollusca 

 of the estuary beds of the same locality are figured in this 

 plate. Potomomya gregaria (\),Potamides concavus (2),Mela- 

 nopsis fusiformis (3), J\I. brevis (4), Neritina concava (5), 

 Melanopsis carinata (6), Potamicfes plicatus (8) and P. ven- 

 tricosus (9), Helix globosus (7). 



681. The fauna of the upper stages of the tertiary forma- 

 tion approaches yet more nearly to that of the present epoch. 

 Besides the pachyderms, that were also predominant in the 

 lower stage, we find numbers of carnivorous animals, some 

 of them much surpassing in size the lions and tigers of our 

 day. We meet also gigantic edentata, and rodents of great 

 size. 



682. The distribution of the tertiary fossils reveals to 

 us the important fact, that in this epoch animals of the same 

 species were circumscribed in much narrower limits than 

 before. The earth's surface, highly diversified by mountains 

 and valleys, was divided into numerous basins, which, like the 

 Gulf of Mexico, or the Mediterranean of our day, contained 

 species not found elsewhere. Such was the basin of Paris, that 

 of London, and hi the United States, that of South Carolina. 



683. In this limitation of certain types within certain 

 bounds, we distinctly observe another approach to the actual 

 condition of things, in the fact that groups of animals which 

 occur only in particular regions are found to have already existed 

 in the same regions during the Tertiary epoch. Thus the 

 edentata are the predominant animals in the fossil fauna of 

 Brazil as well of its present fauna ; and the marsupialia were 

 formerly as numerous in New Holland as they now are, though 

 they were in general of much larger size. 



684. THE MoDEEBT EPOCH. Reign of Man. The present 

 epoch succeeds to, but is not a continuation of, the Tertiary 

 age. These two epochs are separated by a great geological 

 event, traces of which we see everywhere around us. The cli- 

 mate of the northern hemisphere, which had been, during the 

 Tertiary epoch, considerably warmer than now, so as to allow 

 of the growth of palm-trees in the temperate zone of our time, 



