WHITE.] LARAMIE FOSSILS OF YAMPA VALLEY. 207 



are very valuable for general applieatioii, the known great vertical range 

 of some of the species makes it impracticable to place implicit reliance 

 upon any single species as indicating a detinite limited horizon within 

 the gronp. The following comi)arisons and references ^n\l show how far 

 the paleontological indications agree with the known stratigraphical 

 liosition of the fossils in qnestion. According to onr present knowledge 

 of the range of the species of the Fox Hills (ironp, the presence of 

 t^cfq^hites iiorlosus among these fossils indicates for tliem a Ioav horizon in 

 the Fox Hills Gronp, as does also Thetis f circularis, if that species has 

 been correctly identilled. 



On the other hand, all the others may be regarded as ranging through 

 the whole uj^per half of the Fox Hills Gronp in Colorado, and some of 

 them below it, including I>VfC?f?/fes oratufi, which, as before stated, ranges 

 higher upon the Avest side of the Eocky Mountains than it is knoAAni to 

 do upon the east side. Besides this, Inoeeramvs pertenuh^ Avhich is 

 doubtfully identified here, is a species hitherto known only in the upper- 

 most strata of the Fox Hills Group in the Upper Missouri Eiver region; 

 and a variety of I. harahini also exists in the same strata. Summing 

 up the whole paleontological evidence then, it is seen that while it is 

 suggestive of a lower horizon, there is nothing to prove that the strata 

 containing these fossils may not really belong, as they appear to do, to 

 the ux^permost portion of the Fox Hills Groui). Therefore we need not 

 assume that the strata of the last named group were in any degree re- 

 moved by erosion in this neighborhood before the deposition of the 

 Laramie strata. Careful examination at the junction of the two groups 

 in the neighboring hillsides also failed to discover any plane of demark- 

 ation between them. This fact has the same general application in this 

 region west of the mountains that it was found to have at their eastern 

 base. 



J^o other fossiliferous horizons were found in this neighborhood, either 

 in the Fox Hills or Laramie Groups. My journey led me down the val- 

 ley of the Yampa, during which 1 passed much of the way over Laramie 

 strata, as determined bj" their stratigrai^hical position and character- 

 istics, as far down as opposite the confluence of Williams Elver before 

 I found any fossils to confirm those previous conclusions. From this point 

 to one about seven miles below, in the north A^alley side of the Yampa, 

 I found somewhat frequent exposures of fossiliferous layers, the prin- 

 cipal of which was found in Canon Park, a portion of Yampa Valley. 

 The fossils collected here will be treated as from one locality, because 

 they are practically ux)on one horizon and essentially the same species 

 of fossils occur at each locality, except two or three limited ones, where 

 no others besides the Ostrea were found. 



LIST OF LAKAMIE FOSSILS COLLECTED LST TAMPA VALLEY, NEAR 

 CANON PARK, NORTHWESTERN COLORADO. 



1. Ostrea (jlahra Meek & Hayden. 



2. Anomia micronema Meek. 



3. Anomia grypliorliynclius Meek. 



4. Yolsclla (Brachydontes) regularis White. 



5. Corh'wula occidentalis Meek & Hayden. 



6. CorhicuJa (Lejitesthes) fracta Meek. 



7. Corhnla suhtrifjonalis Meek & Hayden. 



8. JS'critina volvilineata ^Yhite. 



9. Mclaiiia wyominfjensis Meek. 



10. Vi'vqyarus pUcajyressiis White. 



11. Campeloma multistriata Meek & Hayden. 



