REVIEWS 107 



not override the ridge land to the north and that the bowlders above 

 referred to do not indicate the former extension of the ice sheet to 

 that point. Although it has lately been pointed out that the ice sheet 

 extended beyond the head waters of the Osage river in Kansas, it is 

 thought very improbable that these bowlders could have been carried 

 that distance on ice floes. The more reasonable explanation of their 

 present location is through icebergs or floating ice carried from the 

 Missouri river on back-water caused by an ice-jam below the mouth 

 of the Osage. This is the present accepted explanation of their origin. 

 Other explanations, such as changes in the course of the river, have not 

 proved tenable. 



Accepting the above explanation of the source of the bowlders, it 

 leads to the important conclusion that the channel of the Osage river 

 was, in part at least, defined prior to the glacial period. The history 

 of the Osage river, with its meandering course as it flows between 

 steep cliffs on either side, has presented to the geologists of Missouri 

 a very interesting problem in physiography, and one which has not 

 yet been settled. It is hoped that this occurrence of glacial bowlders 

 will be of some assistance to the next physiographer who undertakes 

 to read the history of the river. 



Age of the Atlantosaurus Beds. By Willis T. Lee. 



The paper deals with the southern extension of the Atlantosaurus 

 beds along the eastern foothills of the Rocky Mountains into New 

 Mexico, and shows that certain shales in the Canadian Canyon are 

 probably equivalent to these beds. The shales are also traced south 

 and east from their type localities through a new Dinosaur locality 

 and into Oklahoma, where shales, which are apparently the continua- 

 tion of the Dinosaur beds, contain fossils of Lower Cretaceous type. 

 The observations thus tend to confirm the opinion held by many 

 geologists that the Atlantosaurus beds are of Lower Cretaceous age. 



O71 the Porphyritic Appeara?ice. By Alfred C. Lane. 



There are some five different kinds of phenocrysts, or crystals, 

 which may give a porphyritic appearance, viz : 



Coarser relics of a previous consolidation. 



Crystals whose formation took place during the migration of the 

 igneous magma. 



Crystals which were formed early in the process of cooling and 



