552 HISTORICAL PALEONTOLOGY. 



Cheiroptera, Rodentia, and Insectivora. No traces, however, have 

 hitherto been found in the Eocene of the orders Probostidea 

 and Edentata, and the Quadrumana are represented only by 

 two doubtful forms. The Marsupials are represented in 

 the Eocene by Didelphys, the Sirenia by Halitherium, and 

 the Cetaceans by the singular and aberrant family of the Zeu- 

 glodonts. The Ungulates are represented by a great series of 

 forms, of which the most important are the two extinct groups 

 of the Palaotherida and Anoplotherida, the former representing 

 the Perissodactyles, the latter the Artiodactyles. Besides these, 

 however, there occur numerous other extinct forms, chiefly 

 referable to the genera Coryphodon, Lophiodon, Chceropotatnus , 

 Anthracotherium, Hyopotamus, Pliolophus, Dichodon, Dichobune, 

 Xiphodon, &c. 



The Carnivora are represented by the extinct Hyanodon, 

 the Cheiroptera by species of the existing genus Vespertilio, the 

 Rodentia by Shrew-mice (Myoxus), and the Insectivora by 

 Spalacodon. 



CHAPTER LV. 



MIOCENE PERIOD. 



ROCKS OF THE PERIOD. 



THE Miocene formations comprise those Tertiary deposits 

 which contain less than about 35 per cent of existing species 

 of Mollusca, and more than 5 per cent, or those deposits in 

 which the proportion of living shells is less than of extinct 

 species. The Miocene formations are divisible in Europe into 

 a Lower Miocene and Upper Miocene group. 



I. LOWER MIOCENE. The Miocene formations are very 

 poorly represented in Britain, their leading development being 

 at Bovey Tracy, in Devonshire, where there occur sands, clays, 

 and beds of lignite or woody coal. These strata contain nume- 

 rous plants, among which are Vines, Figs, the Cinnamon-tree, 

 Palms, and a number of Coniferce. Other plant-bearing strata 

 in the Hebrides, on the west coast of Scotland, have been 

 referred to the Miocene age. 



In France, the Lower Miocene is represented in Auvergne, 

 Cantal, and Velay, by a great thickness of nearly horizontal 

 strata of sand, sandstone, clays, marls, and limestones, all of 



