266 Annals of the Carnegie Museum. 



searching it carefully for fossils, but without success. It appears to 

 be the same kind of thinly-laminated fine sand and clay which occurs 

 in the Missoula Valley below Missoula. It was evidently deposited 

 in quiet waters. Whether or not it was formed at the time when the 

 many terraces and water-lines were made on the hills and mountains 

 on the sides of the Missoula and Bitter Root valleys is yet to be 

 ascertained. These have suggested a lake which was dammed by a 

 glacier in Quaternary times, but I do not know that the dam has 

 ever been definitely located. Judging by all the other valleys of 

 western Montana, there should be Oligocene and Miocene deposits 

 here, though they may be mostly eroded away or covered by other 

 deposits. 



As it was getting uncomfortably near winter in the mountains, and 

 as I had yet (should the weather permit) to collect the fossil mammals 

 which had been found in North Dakota, there was not time for further 

 explorations on the Flathead Indian reservation. Fortunately the 

 weather in North Dakota remained comparatively warm and pleasant, 

 so that a busy month was spent in collecting fossil mammals, and we 

 returned to Pittsburgh late in December. 



Part II. Notes on the Mesozoic and Cenozoic Geology of 

 North Dakota and Montana. 



The extensive tract of country, to portions of which the following 

 geological observations apply, may be divided into six distinct geolog- 

 ical and physiographic regions. 



I. Northwestern Minnesota. — This is an undulating, partly wooded 

 plain. The underlying Archaean and Paleozoic rocks are overlaid by 

 glacial deposits, and the surface shows the usual physical characters of 

 the drift-regions, viz., low hills, moraines, marshes, ponds, lakes, and 

 comparatively slow-flowing streams. The timber consists of evergreens 

 and deciduous trees. i 



II. Eastern and Northern North Dakota and a Small Portion of 

 Northwestern Minnesota. — This is a grassy prairie, which is wooded 

 only along the streams and near the borders of some of the larger 

 lakes. This region may be divided into two portions : (a) the bed of 

 the glacial Lake Agassiz, a rich, level tract of country with timber 

 only along the few sluggish streams ; and (/;) the remaining portion 

 of North Dakota east and north of the Missouri River. This portion 

 of the country is nearly covered with glacial drift, which is underlaid 

 by rocks of Cretaceous and Tertiary age. 



I 

 I 



