STRATIGRArHICAL GEOLOGY. 477 



After a historical introduction and exhaustive enumeration 

 of the previous scientific literature in any way connected 

 with the area, Richthofen describes the general surface con- 

 formation of the area, and gives the reader a clear conception 

 of the topographical idiosyncrasies of the areas under examina- 

 tion. Then follows a description of the formations and rocks, 

 which omits nothing of lithological, mineralogical, or palseon- 

 tological interest or significance. Richthofen arranged the 

 various members under two divisions of Trias in the same way 

 as in his treatment of the Vorarlberg rocks : 



T . f Upper Dolomite, Dachstein lime- 



\ stone, and Heiligkreuz strata. 



Upper Trias. 



Raibl marls. 



Schlern dolomite. 



St. Cassian marls. 



Cipit limestone. 



Wengen shales and tufaceous rocks. 



Buchenstein nodular limestone. 



Mendola dolomite. 



Virgloria limestone. 



Campil sandstones, etc. 

 Lower Trias. ! Seis limestones. 



Groden sandstones. 



The superposition of the rocks, their surface extension, and 

 the local variability in their development, along with other 

 points of stratigraphical importance, are then carefully dis- 

 cussed. Excellent geological sections show the parallelism of 

 the succession in the different lines of section. The occur- 

 rence of the augite porphyrite is described, with reference both 

 to contemporaneous and intrusive flows. 



Upon the basis of the tectonic structure, and the distribution 

 and development of the formations, Richthofen tries to 

 discover the historical succession of events during Triassic 

 time in South Tyrol, and more especially to determine the 

 elevations and subsidences of the sea-floor in that area. In 

 opposition to Buch and Elie de Beaumont, Richthofen 

 attributes most of the changes in the form of the ground, and 

 also tectonic disturbances to slow crust-movements. He also 

 discusses the formation of the dolomite masses (ante> p. 250). 



