528 E. RUSSELL LLOYD AND C. J. HARES 



The fossils found in the lower part of the Lance in the western 

 Dakotas consist of plant impressions and bones of reptiles. The 

 plant remains are not abundant, but a few good collections have 

 been made from widely separated localities. All of the species 

 belong to the widespread Fort Union flora. The vertebrates 

 include turtles and several genera of dinosaurs, among which is the 

 large-horned Triceratops, which is diagnostic of the Lance forma- 

 tion. The Ceratopsian remains are especially abundant near the 

 base of the formation in the Standing Rock Indian Reservation, 

 but on Little Missouri River several specimens of Triceratops 

 have been found near the top of the formation and stratigraphically 

 below the Ostrea glabra zone. 



Ludlow lignitic member. — The Ludlow lignitic member of the 

 Lance formation occupies a large area in Harding County, South 

 Dakota, and has been mapped northward into Bowman and Billings 

 counties, North Dakota, and eastward into Perkins County, South 

 Dakota, where it merges with the Cannonball marine member. 

 In the vicinity of Ludlow, South Dakota, its type locality, it con- 

 sists of 350 feet of loosely consolidated buff and cream-colored 

 calcareous sandstone and shale with interbedded lignite. It 

 contains most of the lignite of South Dakota and the presence of 

 this lignite is one of the chief criteria for considering it a distinct 

 member of the Lance formation. Its lithologic character in South 

 Dakota is very like, and its fossil flora so far as determined is 

 identical with, the Fort Union. Its flora is like that of the lower 

 part of the Lance, but its lithology is quite different. On the 

 other hand, in North Dakota its flora has the same affinities as in 

 South Dakota, but hthologically it resembles the lower part of the 

 Lance, except for the presence of the numerous lignite beds. It 

 is this variation in color and Hthology of the Lance that renders its 

 separation from the overlying Fort Union so difficult. 



The following sections show the hthologic character of the 

 Ludlow lignitic member. 



