277 
Wuere Do rHe Lance Creek (‘‘Crrarops’’) Brps BELone, 
IN THE CRETACEOUS OR IN THE TERTIARY? 
By OLIveR P. Hay. 
CONTENTS. 
PAG 
HBTS COTICAIMENCSUING epee fae otras tater his ernie date cts ieie eke Oly nal oerer ede aedey-heteWone oka baneine as kh 
2. Necessity for accurate correlation of the primary divisions of the geological column 
AMATHERG ELEM ECOMPIMEM US cra ee eae oe Gacke See mien Ore ie es che) erarferei chacerterra amateksl@eneds 279 
3. The primary divisions are not usually indicated by great unconformities.......... 280 
4. The principal divisions of geological history are based on fossil organisms........ 283 
5. The value of plants as indices of geological dates ...........-...-20eee eee rece 286 
6. Completeness of record of animal life as compared with that of plant life........ 288 
7. The beginning of the Hocene in Europe and America .........................-- 289 
8. Relationships of fauna of Lance Creek epoch to those of Puerco and Torrejon .... 290 
Hishes tailed ‘amphibians; CH@mpSOSaurUs) ovis creel olde eo sls olen 296 
Gracodules stun lesion, a meee eee tees ore sere opcncie ela aie aba Mel ciisaat sh seek cee hots perauick sie s 297 
Dinosaurs... .. nS Nes cll, EN en Pic ONAN CRUCACP CRC CDSN Iga ae aoe eee 299 
9. Relationships of Lance Creek fauna to that of the Judith River epoch ........... 295 
COMMIT CLUSTONSy cis ested ce e+ tote oh See Be ot eee eer us Fa ice op cn en Oet ech Hee aE a ance egE 303 
HisToricaAL RESUME. 
Ever since the beginning of our knowledge of the geology of the West- 
ern plains and the Rocky Mountains there have existed contentions re- 
garding the various deposits to which the names Laramie and Fort Union 
have been applied. ‘These contentions have concerned the grouping of the 
various beds, the geological horizons to which the deposits of different 
basins and of different levels should be referred, and the members to 
which the names Laramie and Fort Union respectively should be re- 
stricted. Up to about the year 1896 certain deposits in the Judith River 
basin and others in Montana, Wyoming, Colorado and New Mexico were 
all regarded as the products of a single geological epoch and were all 
‘alled Laramie. Although as early as 1860, or even earlier, some geolo- 
gists, especially Dr. F. VY. Hayden and Professor Leo Lesquereux, basing 
their opinion on the fossil plants, held that all or the greater part of the 
deposits in question belonged to the Tertiary, the prevailing opinion up to 
1896 was that the Laramie, taking the term in its widest sense, was the 
uppermost portion of the Cretaceous. It may be said, however, that Pro- 
fessor Cope in his great work “The Vertebrata of the Tertiary Forma- 
tions of the West” referred the Laramie, as well as the overlying Puerco 
