82 The American Geologist. February, 1903. 
rcct one. Room is left for doubt only by the absence of 
fossils."" 
We will now return to professor Cope's report on these 
marls. 
In discussing these marls, Cope says : "The fauna of this 
formation is different from that of the other Eocenes in the 
presence of a saurian Champsosaurus, which is characteristic of 
the Laramie Cretaceous, and of marsupial mammals {Ptilodns 
and Calopsalis) which are remains of a type otherwise known 
as Jurassic."*^ 
Cope again says : 
"As already remarked, the Puerco marls may belong to the 
Eocene series in view of their strict conformability to the sup- 
erincumbent rock of that age. But they may represent the Fort 
Union or lignite beds of the Upper Missouri some of whose 
strata they resemble in color and consistence. They contain 
no lignite nor coal, although their occasional black color may 
be due to a small amount of carbonaceous matter.""* 
Where to place these marls is a more difficult proposition 
now that we have read the conclusions and the remarks of the 
above geologists. Dr. Smith says that they lie conformably 
on the Laramie. Endlich states that they are conformable with 
the Fox Hills, and should be assigned a position at the base 
of the Tertiary, room, he says, only being left for doubt by the 
absence of fossils. Cope finds fossils and finds them to be of 
Laramie or earlier age, and concludes that they may represent 
the Fort Union beds which they resemble in color and con- 
sistence. 
Had Cope gone farther south, or a little farther east in his 
explorations, he would have found that these beds contain 
more and more carbonaceous matter as lower portions of the 
series are exposed till they grade insensibly into the Fort Un- 
ion brown coal series, observed by Mr. Oscar Loew near Naci- 
miento; but, as Mr. Cope states in his report, "The expedition 
was abandoned at this point'' and he said his party went to 
the San Juan country, thus leaving the position of these marls 
unsettled. 
To consider the position of these marls further, where the 
Fort Union (Laramie) is wanting they lie apparently con- 
formable upon the Fox Hills; but do not grade into them. 
