H. S. Lull — Mammals and Horned Dinosaurs. 333 



vertebrates in clays above a forty-foot bed of massive sandstone 

 over 400 feet above tbe highest fossiliferous Fox Hills horizon in 

 that particular section. The fact remains, however, that the fos- 

 siliferous portion of the ' Ceratops beds ' is mainly the upper por- 

 tion, the highest point at which dinosaurs were found, being only 

 100 to 150 feet below the Fort Union." 



On the east side of the deposits, according to Hatcher, near 

 Buck Creek the dip of the strata is about 16° JST. W., whereas 

 at the southwestern corner of the area between Twentymile 

 and Little Lightning creeks it increases to 29° N.W. Our 

 own observations, taken not far from the first mentioned place, 

 gave a dip of about 10°. As one mounts the divide toward 

 the west he crosses the entire section, for the slope beyond the 

 summit practically coincides with the dip, so that no further 

 exposures are seen except in the canyons. Bearing this in 

 mind, if the localities of the ceratopsian skulls are at all accu- 

 rately placed upon the map, they would seem to range through 

 nearly the entire Lance formation, provided the lower 400 feet 

 of non-fossiliferous sandstones belong to the Fox Hills {vide 

 supra, p. 332). 



Stratigraphy of the Lance Formation 



The sections which have been recorded from the Niobrara 

 County area are six in number, and may be described as 

 follows : 



1. Beecher's section, 1889. — This, a sketch section by Pro- 

 fessor Beecher, runs approximately north and south, was 

 taken east of Lance Creek, and covers a distance of about 8 

 miles. It was not published but I find it in a letter addressed 

 to Professor Marsh and bearing the date of July 28, 1889. 

 This section, together with a smaller one at Mammal Quarry 

 No. 7 (map, +7), is here shown (figs. 3, 4). It shows two 

 distinct levels where mammals have been found, one near the 

 middle of the section, the locality of the so called Quarry No. 

 7, and the other at the top of the section at Quarry No. 1 

 (map, fig. 2, p. 331, + 1). In each instance the mammal-bear- 

 ing horizon will be seen immediately to overlie a bed of lignitic 

 shales. Quarry No. 7 is also shown in the smaller section and 

 lies in a canyon 30 feet in depth, tributary to Lance Creek on 

 the eastward side. Beecher says of it (letter of July 28, 1889) : 



" We have also found another locality where the mammals are 

 in place and it gives promise of furnishing more bones and jaws 

 than have yet been seen. The sandstone is so soft and friable, 

 however, and the bones so brittle and checked that it will be 

 very difficult to save the specimens. The horizon is much lower 

 than either Quarry No. 1 or Peterson's quarry. The following 

 section shows its position. It lies at the base of a stratum of 



