UTAH ACADEMY OF SCIENCES 29 
forms; on the contrary, such forms as Viviparus, show 
clearly the brackish-water nature of the fauna. Not only 
that, but also a transition to the fresh-water forms of 
the Tertiary. 
Again, all these fossils will be found referred to the 
Laramie by Meek in his memoir on Cretaceous invertebrate 
palaeontology (Vol. 9 U. 8. Geol. Surv. 1876). Dr. White 
also, through his more recent researches, corroborated the 
deduction of Mr. Meek, and it has been on these palaeonto- 
logical grounds that I, as well as others, have referred the 
Book Cliff Coal Series to the Laramie. 
Let us see now what reasons Mr. Richardson brings 
forth to lead him to relegate them to the Mesa Verde. In 
the type locality the Mesa Verde lies conformably between 
two marine Cretaceous formations, the Mancos and Lewis 
Shales. From the faunal relations, the Mesa Verde has 
been definitely placed in the Pierre division of the Mon- 
tana Group. It is overlain by about 1800 feet of the 
marine Cretaceous strata. In the Book Cliffs, Richardson 
claims that there has been a long period of emergence, 
enough time, indeed, to wash 2000 to 3000 feet of Laramie 
and 1800 feet of Lewis Shale into the sea before the Eocene 
was deposited. 
Does observation substantiate this? I think not. Near 
Castlegate the only unconformity that can be found is at the 
top of the Fox Hills Formation. From this line of demar- 
cation the strata have been laid down with a succession 
so gradual that the upper delimiting line can only be found 
by palaeontological means with any degree of certainty. 
This line has been found to correspond to a stratum 
of limestone that is persistent throughout the entire field. 
In Ivy Creek where the Tertiary is covered, in part at 
least, by a basic lava flow, I was enabled to locate the top 
of the Laramie by recognizing this limestone with its 
contained Viviparus paludinaeformis. 
Mr. Richardson gives a good general section of the 
Laramie as I have found it. The only assignable reason 
for assuming that so great an unconformity exists, must 
be that he first assumed the series Mesa Verde and used 
