GEOLOGY AND PALEONTOLOGY. 167 
Since the statement of Doctor Williston, quoted above, two vertebrate fossils 
have been found in the Dakota. Prof. C. S. Parmenter has recently described a 
fossil turtle found south of Concordia.®*! The fossil cast is composed of the 
characteristic red sandstone. It is eleven inches long, nine inches wide, and con- 
tains the well-defined impressions of fourteen ribs. 
On August 27, 1899, the writer found, at the High banks along the Missouri 
river, a mile above Decatur, Neb., a reptilian vertebra. The fossil was found 
embedded in a bank of yellowish clay near the water’s edge. The centrum of 
the vertebra is 70 mm. long, 55 mm. wide, constricted to 35 mm. in the middle, 
the ends being but slightly concave. Doctor Williston, to whom the fossil was 
submitted, was unable, on account of its imperfect state of preservation, to iden- 
tify it with certainty, but considered it the vertebra of either a crocodile or a 
dinosaur. 
CONCLUSION. 
The Dakota Cretaceous as a group is widely but not thoroughly known. Its 
history dates from 1804, when Lewis and Clarke first described the hills of soft, 
yellow sandstone near Sioux City. The controversy concerning the age of the 
group, waged by Meek, Hayden, and Newberry, against Swallow, Hawn, Marcou, 
and Heer, occurred from 1855 to 1864. The men who have written most exten- 
sively concerning the group, besides those just mentioned, are White, Ward, 
Hay, Mudge, and especially Leo Lesquereux. 
The Dakota extends from southwest Kansas to northeast Nebraska, along a 
line over 500 miles long. The region of outcrops along this line approximates 
thirty miles in width. It reaches its greatest development in central and north- 
ern Kansas. ‘To the northeast and southwest of this region post-Cretaceous 
erosion and deposits have so modified the Dakota that the outcrops are usually 
restricted to lines of bluffs or isolated exposures. 
The rocks of this group rest either conformably on the Comanche Cretaceous, 
or unconformably on the Permian or Carboniferous. The line of demarkation 
between the Comanche and the Dakota has not been sharply drawn; and, in the 
light of our present knowledge, such a line is impracticable. The Dakota grades 
upward into the Benton wherever the latter is present; otherwise the upper limit 
is marked by a line of unconformity below Cenozoic rocks. The stratigraphy 
of the group has not been well understood. Instead of consisting almost exclu- 
sively of sandstone, it is found that the greater part of the entire thickness is 
composed of clays and shales. There is no general continuity of strata, the vari- 
ous members appearing and disappearing without seeming regularity. The 
origin of the rock is probably estuarine or beach deposits under changing condi- 
tions of elevation. Besides the ordinary forms of stratigraphy, many peculiar 
phases may be observed, such as concretions, gravel-beds, quartz-like ledges and 
the like. 
The stone of the Dakota is used for building purposes to only a limited 
extent. The clays, however, are destined to become an important economic fac- 
tor. An excellent quality of brick and tile has been manufactured from this clay 
in several localities. Coal is mined in limited areas in northern Kansas, but is 
inferior both in quality and quantity. Sand is plentiful but is not in great demand. 
The few deposits of gravel in the formation are being utilized by railroad companies. 
The water-supply is inexhaustible. The Dakota sandstone is the great water 
holder of the plains. The origin of the water has been assigned to three sources, 
viz.: Artesian flow from the mountains, sheet water, and local rainfall. Springs 
are everywhere present and constitute an important economic phase of the group. 
61. Loc. cit., 16: 17. 
