During Triassic and Jurassic Periods 203 



Chara, Cypris, Bithynia, Planorbis, Corhula^ and Hyd- 

 robia, along with teeth scales and bones of fishes, all of 

 which he regards as freshwater. 



J. V. Rohon {16:1) gives a valuable glimpse into 

 freshwater beds that he and Heer regard as of Upper 

 Liassic age, and which are exposed on the Angara river 

 north of Irkutsk in Siberia. In contrast to the extensive 



Fig. 27 



Fig. 27. Dapedius politus, a freshwater Lower Liassic ganoid 

 fish from Dorset, England. Fig. 28, restoration of the skeleton; 

 both one-fourth natural size. (After A. S. Woodward). 



