THE MIOCENE PERIOD. 



305 



dence of the existence in Europe at this period of examples of 

 the orders of the Gnawing Mammals (Rodent ia), the Insect- 



Fig. 233. Portion of the skeleton of Vespertilio Parisiensis. Eocene Tertiary, France. 



eating Mammals (Insect ivora), and the Monkeys (Quadru- 

 mana).* 



CHAPTER XIX. 



THE MIOCENE PERIOD. 



The Miocene rocks comprise those Tertiary deposits which 

 contain less than about 35 per cent of existing species of shells 

 (MffUusca), and more than 5 per cent or those deposits in 

 which the proportion of living shells is less than of extinct 

 species. They are divisible into a Lower Miocene (Oligocene) 

 and an Upper Miocene series. 



In Britain, the Miocene rocks are very poorly developed, 

 one of their leading developments being at Bovey Tracy in 

 Devonshire, where there occur sands, clays, and beds of lignite 



* A short list of the more important works relating to the Eocene 

 rocks and fossils will be given after all the Tertiary deposits have been 

 treated of. 



