386 Professor Buckland on the Bones of Mastodon, Sgcfrom Ava. 



tliree hundred miles of the course of the Irawadi, from Prome to A.va, present 

 a repetition of the geological structure of Europe. 



From the examination of the specimens, compared with the notes in Mr. 

 Ci-awfurd's journal, the following formations maybe recognised with a greater 

 or less degree of certainty. 



1. Alluvium. 



2. Diluvium. 



3. Freshwater Marl. 



4. London Clay and Calcaire Grossier. 



5. Plastic Clay, with its sands and gravel. 



6. Transition Limestone. 



7. Grauwacke. 



8. Primitive Rocks, Marble, Mica Slate. 



There are also indications (but less certain) of new red-sandstone and 

 magnesian limestone. 



The Alluvium and Diluvium (Nos. 1. and 2.) have been already spoken of. 



3. The Freshwater formation (No. 3.) occurs a little north of the Petro- 

 leum Wells and of the district in which the bones were found near Wetma- 

 sut, and is at an elevation of 150 feet above the Irawadi. The specimens 

 of it consist exclusively of marly blue clay containing freshwater shells of the 

 genus Cyrena : the shells are very thick and heavy, nearly three inches in 

 diameter, and judging from the great quantity imported, must be extremely 

 abundant ; and, though accompanied by no other organic remains of any kind, 

 are sufficient to establish an analogy, in the strata containing them, to the 

 freshwater formations that occur associated with the tertiary strata of Europe. 

 There is, however, no evidence to show any connexion between these fresh- 

 water deposits and the fossil bones or wood ; from the portions of iron and 

 gravel adhering to many of the remains of tortoise, crocodile and hippopota- 

 mus, it should seem that they had no connection with the freshwater deposit : 

 still the abundance and size of such animals show that there must have been 

 large rivers or lakes at the time and place in which they lived ; though it 

 would not justify our assigning them, without further examination, to the 

 period in which these freshwater strata were formed that contain the shells 

 of Cyrena. 



4. We have from the hills near Prome a coarse-grained yellow shelly and 

 sandy limestone, scarcely distinguishable from the calcaire grossier of Paris ; 

 and from several places higher up the Irawadi, particularly at Pagan, we 

 have a dark bituminous slaty limestone, in which Mr. Sowerby has recognised 

 the following fossils as identical with those of the London clay. 



