this epoch for the first time we come across remains of 

 animals- and plants allied to those of the present time. The 

 trilobite of the Silurian period, the peculiar bony-armoured 

 fish of the Red-sandstone, the large club-mosses and reeds 

 of the carboniferous system, the huge reptiles of the Oolite, 

 the Ammonites of the Lias and the chalk, give place to new 

 forms of life. Only 3 to 4/ c of the Tertiary plants and 

 animals of the earliest strata are modern ; about .18% of 

 the plants and animals of the middle tertiary period are 

 modern, and there is no distinct gap between the close of 

 the tertiary period and the recent period. The lowest tertiary 

 period is called Eocene when the existing forms of life are first 

 seen. The middle period is called Miocene^ and the uppermost 

 tertiary period is called Pliocene. The nummulitic limestone 

 formations of the Himalayas often attaining a height of 

 16,000 ft. are marine and Eocene. Mammals appeared first 

 in the Miocene period, and the extensive fossil remains of 

 the Siwalik range belong to this period. The Sivatherium 

 deer is the characteristic fossil of this period. Gangetic 

 crocodiles and land turtles of modern times also occurred, 

 also a huge but extinct species of tortoise a shell of which 

 can be seen in the Indian Museum. In the Pliocene period 

 man first made his appearance, and agate knives have been 

 discovered in the upper Godavery characteristic of this period. 

 The greatest depth of the Tertiary group of rocks is 9,000 ft. 



7//z. Between the Indus and the Brahmaputra there lies 

 a vast alluvial plain which consists mainly of Miocene and 

 Pliocene Tertiary deposits. These are the Recent Forma- 

 tions, the commencement of this period being co-eval with 

 the first appearance of man. In Bengal, though some of the 

 other systems are represented, as we have already indicated, 

 we are mainly concerned with these alluvial post-tertiary 

 and recent deposits. The post-tertiary Glacial or Pleisto- 

 cene period is probably not represented in Bengal, except at 

 the Himalayas down to a height of 3000 ft. 



