428 ■ PROCEEDINGS OF THE ACADEMY OF [1897. 



large area. It appears as a compact rock of light or gray color, some- 

 times yellowish, of which the typical varieties have the property of 

 disintegrating into minute particles with angular points and curiously 

 curved surfaces. Fossils are extremely rare in these beds. Along- 

 side of the teeth of squali. spiculse of sponges and of radiolaria, are 

 found the shells of Lingula, prints of shells of Lima nucata, and the 

 sponge Botroclonium spasski. Various considerations have induced 

 the Russian geologists to ascribe these beds to the Eocene. 



To the east of these silico-argillaceous beds are widely distributed 

 sandstones slightly coherent, accompanied by -sands and clays. In 

 these deposits are found well-preserved remains of fishes : Lamna 

 elegans, L. cuspidata, L. denticidata, Otodus macrotus, Notidanus 

 serratissimus, Galeocerdo minor, Actobatis, Myliobates etc. Besides 

 this the remains of mollusks have been found; the species most 

 widely distributed — Cyprina — resembles very much C. perovalis. 

 In addition occur Modiola, Psammobia (?), Fusus (Neptunea) 

 gracilis, F. multisulcatus and Naidica sp. The above are classed as 

 Oligocene. 



Among the most remarkable deposits of post-tertiary age of the 

 east slope of the Oural besides the glacial deposits developed north 

 of the 61st parallel are the auriferous and platiniferous sands (the 

 latter belonging exclusively to the Ourals). Intimately connected 

 with the serpentines and their primitive rocks, to the disintegration 

 of which the platiniferous groups owe their origin, they are not so 

 largely developed as the auriferous placers. 



The auriferous placers of the Oural are stratified masses, which vary 

 from a very thin layer to a thickness of 4 meters and more. Gener- 

 ally they vary between 0-5 meters and 1 m. Their longitudinal extent, 

 which is usually 20 to 40 m., often reaches 200 and even 500 m. They 

 are rarely more extensive, though placers of 4J, 6 and 12 kilom. are 

 known (placer Pechtchanka, District Bogoslovsk). Their width is 

 sometimes very small, 2 to 4 metei's; ordinarily it is 20 to 40 m., 

 and has been known 100 m. and more. Sometimes auriferous beds 

 are found on vegetable earth or immediately under the grass, but 

 usually they are covered by barren earth, i. e., an alluvial bed desti- 

 tute of gold, called "turf," because the first placers found in the 

 Ourals were covered by a real turf. The barren earth varies from 

 - 5 m. to 4 m., and occasionally reaches 20 m., and even more. The 

 placers usually rest on hard rock, or that little disintegrated, called 



