BULLETIISr 77, UNITED STATES NATIONAL MUSEUM. 



Table of Cambrian and Ordovician formations in Russia. 

 [After von Schmidt.] 



Formation. 



Ordovician: 



Borkholm limestone 



Lyckholm limestone 



Wesenberg limestone 



Jewe limestone 



Itfer limestone 



Kuckers shale 



Echinospherites limestone 



Orthoceratite (Vaginoceras) limestone. 



Glauconite limestone 



Glaueonite sandstone 



Cambrian: 



Dictyonema shale 



Ungulite sandstone 



Blue clay and associated formations. . . 

 Granite 



von Schmidt's 

 terms. 



Later. Older, 



F2 

 Fl 

 E 

 D 

 C3 

 C2 

 CI 

 B3 

 B2 

 Bl 



A3 

 A2 

 Al 



Zones 

 2a 

 2 

 lb 



Since the publication of the above table three divisions have been 

 recognized in formation D. The Jewe limestone has been restricted 

 to the lower division, Dl; shaly strata succeed the limestone beds 

 of Dl and form the Kegel beds, D2, while D3, consisting of very 

 fossilif erous, thin bedded blue limestones and shales, forms the closing 

 member of the formation. The Orthoceratite limestone is often 

 cited simply as the Orthoceras limestone, and is so designated 

 throughout the present work. 



The long-continued researches of the late Prof. F, von Schmidt 

 upon the Cambrian and Ordovician rocks of the Russian Baltic 

 provinces have resulted in such a detailed knowledge of the geology 

 that the stratigraphic section is now fairly well known. Pander, 

 von Eichwald, de Verneuil, Keyserling, Holm, and Lamansky have 

 contributed in a lesser degree to the stratigraphy, while, in addition 

 to these, von Schmidt, von Mickwitz, von tluene, Jaekel, Koken, 

 Palilen, Dybowski, Wysogorski, and Bonnema have published re- 

 searches on the paleontology of the region. The paleontological 

 work of these authors has not, as a rule, been of a general nature, 

 although Eichwald' s Lethsea Rossica is an important exception. 

 Thus, von Schmidt has elaborated the Ordovician trilobites in great 

 detail, while similarly Koken has monographed the gastropods, 

 Jaekel has studied the cystids, and Dybowski has described some 

 of the monticuliporoids. More recentl}^, Bonnema has pubUshed 

 upon the Ostracoda of the Kuckers shale. 



