
oe. a = 
Py. 
- 
Le ree 
‘ 

AGE OF THE LIGNITE FORMATION. 193 
Prof. Marsh is stated to have found, “over the coal series, six 
‘miles from Green River, near Brush Creek, in Utah, a layer full of Ostrea 
congesta, Con., a typical Cretaceous fossil, and ahkove this a crinoid; per- 
haps related to the Cretaceous Marsupites, and also scales of a Beryx, 
a genus of Cretaceous fishes; and in shales below the coal bed, remains 
of turtles of Cretaceous types, and teeth resembling those of a Megalosau- 
rus.” * These beds, however, according to Prof. Cope, f do not belong 
to the horizon of the lignite formation of Bitter Creek, but perhaps to 
Cretaceous No. 3, and cannot be accepted in evidence for the Cretaceous 
age of the Lignite formation properly so-called. 
446. The Cretaceous age of at least a considerable part of the Lignite 
formation of the West is also held by Messrs. Marsh, Stephenson, Em- 
mons, and King. The latter places the line of division between the Cre- 
taceous and Tertiary at Bitter Creek, at the level of the highest horizon of 
brackish-water shells—a distinction which has the appearance of being 
a purely arbitrary one. 
447. The issue is perhaps closest with regard to these Bitter Creek 
representatives of the formation. By Prof. Cope, they are referred to 
the upper part of the Cretaceous, from the occurrence of the Dinosaurian, 
Agathaumas sylvestris. Prof. Meek, as we have seen, though not without 
much doubt, also relegates them to this formation; while Prof. 
Lesquereux believes the plants to be unquestionably Tertiary and Lower 
Eocene. Prof. Hayden had previously remarked the impossiblity of 
laying down any exact line between the Cretaceous and Tertiary of this 
region, and believes a considerable thickness of “ transition beds” 
to be developed ; { a feature also insisted on subsequently by Dr. Bannis- 
ter.§ Here at least, we find the co-existence of the remnants of a Cre- 
taceous fauna, with a flora such as is usually considered Tertiary by 
paleontologists. 
448. In the above brief summary of facts and opinions, it has been 
endeavored to bring together the more important data bearing on the age 
of the western Lignite formation, and to illustrate the gradual change of 
opinion which has taken place concerning it. For details and illustra- 
tions, it will only be necessary to refer to the elaborate and valuable 
reports of the gentlemen referred to. 
449. The physical nature of the junction of the Lignite-bearing beds, 
and “ transition beds,” with the well marked Cretaceous, has already 

* Manual of Geology. Dana. 1875. p. 457. + U.S. Geol. Surv. Territ. 1873, p. 439. 
} U. S. Geol. Surv. Territ., 1870. p. 75. § U.S. Geol. Surv. Territ., 1872. p. 525. 
13 D 
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