' TWENHOFEL: EXPEDITION TO THE BALTIC PROVINCES. 341 
Part 3.— AN INTERPRETATION OF THE SILURIAN SECTION or GOTLAND. 
INTRODUCTION. 
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 northern 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. 
Without entering into a detailed discussion of the different views 
which 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 
