156 Sioux City Academy of Science and Letters. 
of deposition. From their beveled condition and the 
evidence of great pre-Glacial erosion over the region the 
view is strengthened that they were once present, and 
that there may even have been a thin edge of Fox Hills 
sandstones deposited here in shallow ocean waters. Dur- 
ing Laramie times when great areas to the west and 
northwest contained brackish and fresh-water lakes, 
northeastern Nebraska was probably a land surface, and 
probably it so continued through the Tertiary. 
Undoubted Tertiary outliers are found in Holt Coun- 
ty 75 miles west of Dakota County. These are mapped 
by N. H. Darton as the Arikaree formation, and are over- 
lain in some places by Equus beds. 
No positive evidence has yet been brought forth that 
the Tertiary deposits of Nebraska were laid down as far 
east as Missouri River. Professor Todd* has endeavored 
to show that Lake Cheyenne continued to the Glacial 
epoch and that its eastward extension occupied portions 
of Western Iowa, southeastern South Dakota and east- 
ern Nebraska. He cites a number of instances of the 
presence in this region of fine sands, containing fossil 
bones, overlain in places by lead-colored clay without 
pebbles, also the presence of fossil silt in many places at 
levels lower than those of the drift. The fossil claw of a 
megalonyx was found in sand below the drift in Mills 
County, Iowa, about 100 miles south of Dakota County. 
Professor Todd also cites the occurrence of stratified vol- 
canic ash, apparently deposited in still water just pre- 
ceding the deposition of the drift in some parts and suc- 
ceeding it in others. 
H. F. Bain* in his survey of Woodbury County, Iowa, 
also gave considerable attention to the Tertiary question 
in this region. He found above the Cretaceous and below 
the Glacial deposits at Riverside, Sioux City, beds of fine 
to coarse, white sand containing small pebbles mainly 
granitic. The pebbles were waterworn and not striated. 
They may have come from the west or north, but they 
were not distinctly of northern derivation. The sand 
bore a general resemblance to that of the Miocene or Pli- 
ocene beds to the westward in Nebraska. The only fos- 
aTodd, J. E.,. Evidence that Lake Cheyenne continued till the Gla- 
cial epoch: Proc. Am. Assoc. Adv. Sci., Vol. 37, 1889, pp. 202-203. 
bBain, H. F., Geology of Woodbury County; Iowa Geol. Survey, Vol. 
5, 1895, pp. 276-278. 
Notes on the geology of Northwestern Iowa: Proc. Lowe Acad. 
Sci., Vol. 1, pt. 2, 1892, p. 14. 
