TWENHOFEL: EXPEDITION TO THE BALTIC PROVINCES. 341 



Parts. — Ax Interpretation of the Silurian Section of Gotland. 



INTRODUCTIOX. 



The writer's hope of discovering new facts which might illuminate 

 some of the intricate problems of Gotland's stratigraphy, and of being 

 able to place before American students a detailed section of the strata, 

 is his excuse for delving into this much studied field. The present 

 discussion, which is intended to be preliminary to a more extensive 

 treatment of the subject, attempts an interpretation of the lithic and 

 faunal peculiarities of the stratigraphy. In the first part is given a de- 

 scription of some of the more important features which bear on the 

 problem. This is followed by an interpretation of these features. 

 Lastly, the various conclusions which have been reached are sum- 

 marized. 



In this study of the section, I was greatly assisted by Dr. Henry 

 Munthe of the Swedish Geological Survey, a courtesy which is deeply 

 appreciated. 



Lithic and Faunal Characteristics of the Gotland Strata. 



The Silurian rocks of Gotland have long been famous because of 

 the abundance and excellent preservation of their fossils, and many of 

 the great leaders of European geology have gone to the island as pil- 

 grims to a shrine. The sequence of strata and the faunas have fur- 

 nished the theme of numerous papers, and few of the masters of geology 

 of no-rthern Europe have refrained from in some way referring to the 

 geology of this " Cross Roads of the Baltic." In spite, however, of the 

 fact that numerous students have studied the various sections, there 

 still is much that is uncertain and obscure. This arises from the 

 absence of extensive exposures in the interior of the island, the decided 

 horizontal variation of the sediments and their enclosed faunas, the 

 numerous undulations of the strata, and the extensive discontinuities 

 in the shore sections. 



^Yithout entering into a detailed discussion of the different views 

 w^hich have been held, attention will merely be called to the two 

 divergent lines about which they may be grouped. Murchison (1847) 

 considered that the strata dipped from northwest to southeast, that 

 the beds of North Gotland are the oldest and underlie those of southern 

 and central Gotland. In this view, he was later stoutly supported 



