1897.] NATURAL SCIENCES OF PHILADELPHIA. 427 



procuboides, Orthis striatula, Pentamerus galeatus and the trilobites 

 near the village of Pokrovskoie in the district of Irbit Phacops 

 feeundus, Anarcestes lateseplatus, Pleurotomaria subcarinata, Tenta- 

 culites acuarius. To the upper Devonic may be classed the lime- 

 stones of Lake Koltouban, Montieocerus intumescens, Spirifer dis- 

 junctus, Sp. Archiaci, etc. The Carbonic system is composed of (1) 

 schistose clays and argillaceous schists, sandstones and conglomer- 

 ates, with intercalations of coal and concretions of Spherosiderite. 

 The organic remains are almost exclusively plants (Lepido- 

 dendron glincanum, Stigmaria ficoides). At times the rocks are 

 much metamorphosed, and the carbonic schists are transformed into 

 graphites with vestiges of plants. (2) Limestone with Productus 

 giganteus Pr. striatus, corals, etc. (3) Limestone of the upper 

 horizons, those of Chartymka, the fauna described by Verneuil. 

 Gastrloceras marianxmx, Pronorites cyclolobus var. uralensis. One 

 hundred species of fossils have been found, of which many have not 

 yet been described. (4) Ordinarily the limestone of Pr. gigant. are 

 replaced above by a schistose limestone, or by a coarse conglomerate, 

 in which the fragments of limestone of different sizes are held 

 together by a calcareous cement. The conglomerates are replaced 

 by sandstones covered by marls or argillaceous limestones finely 

 stratified with subordinate beds of limestones sometimes coralliferous 

 (Chcetetes radians) Syringopora parallela, Spirifer mosquensis. 

 Above this is a clay with Gypsum. 



On the east slope of the Ourals are found islets of mesozoic deposits : 

 clays and sandstones containing lignite. In general the fossils are 

 badly preserved remains of plants. (Asplenium whitbiense var. 

 tenuis, Phyllotheca striata, Prodozamites lanceolatus etc. and remains 

 of Estheria minuta var. karpinskyana.') 



Finally on the east slope of the northern Ourals occurs the upper 

 Jurassic, containing Ammonites ; deposits of lower and upper 

 Cretacic with Baculites beds of upper Cretacic with Belemnitella 

 mucronata, Gryphea vesicularis, etc. 



The tertiary sediments are very remarkable. Commencing at 50 

 to 100 kilometers from the axis they extend in horizontal beds which 

 grow continually thicker into the interior of Siberia. The predomi- 

 nant rocks of these sediments in the zone nearest to the Oural are 

 sandstones, presenting sometimes very peculiar characteristics, and 

 particularly, a rock composed of an intimate mixture of amorphous 

 clay with an equally amorphous silica. This material covers a very 



