2 26 White on later Cretaceous deposits in Iowa. 
the region adjacent to western Iowa, I adhered to my previous 
opinion that they were all of earlier Cretaceous age. 
I was influenced by those impressions while discussing in a 
late publication,' the shifting position of the eastern shore line 
of the mesozoic seas -which prevailed in what is now the inter- 
ior of North America. I there expressed the belief that the 
Cretaceous shore line finally receded to the westward of west- 
ern Iowa at the close of the Colorado epoch of the earlier Cre- 
taceous. Now, however, the fossils found in Hardin county 
seem to warrant the opinion that the final recedence to the 
westward of Iowa of the Cretaceous shore line occurred as late 
as the closing epoch of the later Cretaceous. That is, not 
only is the general character of all those Hardin county fossils 
suggestive of their afiinity with the molluscan fauna of the Fox 
Hills group, but two of them have been specifically identified 
with characteristic fossils of that group; and of the specific 
identity of three others there is apparently little room for doubt. 
It is not to be denied that if the fossils discovered in Hardin 
iind Howard counties had been obtained from strata undeniably 
in situ, the evidence furnished by them would be more satisfac- 
tory. It would also be more satisfactory if it were supported 
by a large number of similar discoveries; and in the estimate 
which I put upon the value of these, the anticipation of future 
discoveries, even of strata in situ, is taken into account. Even 
in view only of the discoveries already made in Iowa and -in 
Minnesota, a portion of which have been mentioned in previous 
paragraphs, one can hardly entertain a reasonable doubt that 
considerable deposits of later, as well as earlier Cretaceous strata 
were made far within the present limits of the state of Iowa. 
Although the meridian position of this Hardin county locality 
is more westerly than that of Howard county, it is much more 
easterly than is any other known Cretaceous locality in Iowa 
south of the northern tier of its counties. If, therefore, we re- 
gard the Hardin county fossils as having been originally depos- 
ited where they were found, this discovery materially extends 
the known eastern limit of Cretaceous deposits in that state. It 
is fully believed that those fossils were originally deposited at, 
1 See White, C. A., On the Fresh Water Invertebrates of the North 
American Jurassic. Bui. U. S. Geol. Survey No. 39, p. 14. 
