EAELY PALEOZOIC BEYOZOA OF THE BALTIC PROVINCES. 5 



dated materials. Their strata in certain portions of the Baltic 

 provinces have apparently never been covered by younger deposits 

 and have been so little disturbed that the sediments often have 

 remained as originally deposited. As a result the included fossUs 

 are in an especially fine state of preservation. 



In spite of this apparently undisturbed condition of the strata 

 both the paleontologic and stratigraphic records show great time 

 breaks in the sequence. Thus the entire Middle Cambrian is wanting, 

 and, according to the present results, the greater portion of the 

 North American Ordovician section is absent. 



Fig. 1.— Map of Baltic Sea area, showing DiSTEmTrTioN of OBDOAnciAN and Szlueian steata. (Afteb 



VON Schmidt.) 



The Cambrian and Ordovician strata of the Baltic area have been 

 divided by von Schmidt into six general divisions, designated by the 

 letters A to F. In an earlier classification the same author recog- 

 nized three zones with several subdivisions. The lettered divisions 

 have since had geographic names applied to most of them, although 

 in a few cases a lithologic designation, or the name of a characteristic 

 genus of fossils has been retained. These several classifications are 

 tabulated on the following page. 



