414 GEOLOGICAL SUCCESSION OF ANIMALS. 



678. TEETIART AGE. Reign of Mammals. The most 

 significant characteristic of the Tertiary faunas is their great 

 resemblance to those of the present epoch. The animals be- 

 long in general to the same families, and mostly to the same 

 genera, differing only as to species. The specific differences, 

 however, are sometimes so slightly marked, that a consider- 

 able familiarity with the subject is required, in order readily 

 to detect them. Many of the most abundant types of for- 

 mer epochs have now disappeared. The changes are espe- 

 cially striking among the mollusca, the two great families of 

 Ammonites and Belemnites, which present such an astonish- 

 ing variety in the Oolitic and Cretaceous epochs, being now 

 completely wanting. Changes of no less importance take 

 place among the fishes, which are for the most part covered 

 with horny scales, like those of the present epoch, while in 

 earlier ages they were generally covered with enamel. Among 

 the radiata, we see the family of crinoids reduced to a very 

 few species, while, on the other hand, a great number of new 

 star-fishes and sea-urchins make their appearance. There 

 are besides, innumerable remains of a very peculiar type of 

 animals, almost unknown in the former ages, as well as in 

 the present period. They are little-chambered shells, known to 

 geologists under the name of Nummulites, from their coin-like 

 appearance, and which form in some countries very extensive 

 layers of rocks. 



679. But what is more important, in a philosophical 

 point of view, is, that aquatic animals are no longer predomi- 

 nant in Creation. The great marine or amphibian reptiles 

 give place to numerous mammals of great size. For which 

 reason we have called this age the Reign of Mammals. 



680. The lower stage of this formation is particularly 

 characterized by great pachyderms, among which we may 

 mention the Pal&otherium and Anoplotherium, which have 

 acquired such celebrity from the researches of Cuvier. These 

 animals, among others, abound in the tertiary formations of 

 the neighbourhood of Paris, and those of the Hampshire 

 basin. The Pal&otheria, of which several species are known, 

 are the most common ; they resemble, in some respects, the 

 tapirs, while the Anoplotheria are more slender animals. In 

 America are found the remains of a most extraordinary 

 animal of gigantic size, the Basilosaurus, a true cetacean. 

 Finally, in these stages, the earliest remains of monkeys have 



