534 



THE AMERICAN XAT ERA LIST [Vol. XL 



Bulletin 237 of the United States Geological Survey is a paper by 

 L. V. Pirsson on the "Petrography and Geology of the Igneous Rocks 

 of the High wood Mts., Montana." The report treats mainly the 

 petrography of this volcanic center, with a brief review of the geology 

 of the district. The portion of general interest is the bearing of this- 

 region upon the theories of the consanguinity of lavas. 



