426 PROCEEDINGS OF THE ACADEMY OF [1897. 



MgS0 4 and MgCl r Almost all of these show evidences of gradual 

 drying up. It is worthy of notice that the salinity of the lakes is 

 subject to changes of weather and of the seasons. 



The eastern limit of the crystalline region characterized by lakes 

 of type I is separated from the western boundary of the region of 

 tertiary deposits with the lakes of the steppe by a belt composed 

 partly of sedimentary and partly of massives and elastics (tuffs). The 

 lakes of this belt are characterized by certain characters of each of 

 the foregoing types, i. e., the simple form, and straight and low 

 beaches of the steppe lakes and the rocky islets, and correspondence 

 of the lines of their greatest extension with the strikes of the enclos- 

 ing rocks which are peculiar to the mountain lakes. 



The marshes deserve notice. Some are the beds of old lakes now 

 covered with vegetation. Sometimes the small lakes are covered 

 with a mantle of swampy interlacing vegetation. Others are situated 

 on the belt which divides the rivers, and frequently on the quite 

 steep slopes of the hills, independently of the marshes in evident 

 connection with the lakes. 



Finally there are regions of salt deposits which characterize the 

 east slope of the Oural. The thin sheets of salt which appear from 

 time to time covering even the plants indigenous to saline terraces 

 with a layer of salt, are developed in the saline lake region, but some 

 small deposits are found in the western region and quite high up 

 on the slope. The variation in the distribution of the saline lakes 

 depends not only on the water infiltrated through the soil, but also 

 on the wind scattering the pulverized salt into the lakes for longer or 

 shorter time. 



The rocks most frequently encountered on the east slope of the 

 Ourals are (commencing with the oldest) the lower Devonic (Hercyn. 

 iau), represented by limestones, and containing a fauna described by 

 Tschernischew. Among the characteristic fossils are Eutomis pela- 

 gica, Aristozoe herzinica, Spirifer indiferens, Atrypa reticularis, 

 A. granulifera, Rhynchonella princeps, Rh. nympha, Pentamerus 

 galeatus, P. procerulus, var. gradualis, P. striatus, P. vogulicus, P. 

 pseudoknighti, Slrophomena stephani. The tuffs accompanying the 

 porphyrites contain also organic remains (Pentamerus, Crinoids, 

 etc.). Radiolaria have been discovered by Tschernischew in the 

 jasper of the Ourals. 



The middle Devonic seems to be represented by limestones with 

 corals and stromatopores. Grilnwaldtia latilinguis, Rhynchonella 



