CRETACEOUS AND TERTIARY FORMATIONS 529 



A large number of plants collected from the same formation 

 in the Miles City region are listed by Dr. Knowlton in his discus- 

 sion of this area. 1 



The Lance beds extend up the Tongue river about 50 miles 

 above its mouth, or to within about ten miles of Ashland. 2 



That they extend up the Powder River at least twelve miles 

 above Hackett is indicated by the finding of part of a Triceratops 

 skeleton at that point by Barnum Brown, the bones occurring 

 in dark shale near river level. 3 There is also evidence for believing 

 that the Lance formation appears along the Powder River valley 

 almost if not quite as far south as the Wyoming line, Mr. E. S. 

 Riggs, of the Field Museum of Natural History, having found on 

 the East Fork of the Little Powder River "a weathered skeleton 

 of Trachodon, partial skulls of Ceratopsia and fragments of a 

 large carnivorous dinosaur, probably a Tyrannosaurus. The 

 formation was thence traced along the east bank of Powder River 

 from Powderville to a point on Sheep Creek some miles northeast 

 of Mizpah." 4 



Missouri Valley area. — In Dawson and Valley counties, Mon- 

 tana, the Lance formation is exposed over a large area, bordering 

 the Missouri River from the Musselshell on the west to the station 

 of Brockton on the east. The beds are particularly well shown 

 in the badlands formed by the many tributaries of the Missouri 

 from the south. Among these is Hell Creek, which enters the river 

 south and west of Glasgow, and the formations occurring in this 

 vicinity have been studied and described by Mr. Barnum Brown. 5 

 A massive brown sandstone here forms the basal member of the 

 Lance formation, whereas in south-central North Dakota it is 

 the upper member which is sandstone. The thick black shale 

 member is also absent, but in general there is a strong resemblance 

 between the beds of the two localities. 



1 Proc. Wash. Acad. Sci., XI, No. 3 (1909), 188-90. 



2 C. H. Wegemann, "Notes on the Coals of the Custer National Forest, Mon- 

 tana," Bull. U.S. Geol. Surv., No. 381 (1909), 104. 



3 Bull. Am. Mus. Nat. Hist., XXIII (1907), 823. 



4 Proc. Wash. Acad. Sci., XI, No. 3 (1909), 204. 



s Bull. Am. Mus. Nat. Hist., XXIII (1907), 823-45. 



