742 A. C. PEALE 
upon for the discrimination of horizons within the Cretaceous nor for distin- 
guishing between Cretaceous and Tertiary. 
Fresh-water invertebrates therefore cannot be depended upon 
as time-markers in geologic investigations; still it is true as Stanton 
further says: 
When the investigation is confined to a single region and when the geo- 
graphic and stratigraphic range of non-marine species has been determined 
their evidence is useful and important. 
Therefore, from the viewpoint of the present writer the strati- 
graphic position of the Judith River beds is the same as that of the 
Lance formation, or the lower portion of it; a comparison of their. 
fresh-water faunas is interesting and instructive, because it cor- 
roborates to a considerable extent the more conclusive evidence 
presented by the vertebrates.” 
THE VERTEBRATE EVIDENCE 
Hayden in his early explorations in 1855 collected in the Judith 
River basin, not only marine invertebrates from the Fox Hills 
sandstones underlying the fresh-water fossiliferous Judith River 
beds, but also obtained from the latter, vertebrate remains which 
constitute the first horned dinosaurs of the Ceratopsia ever collected 
in this country. These, and other specimens from near Long Lake, 
N.D., in what is now called the Lance formation, were studied by 
Dr. Joseph Leidy, resulting in the establishment by him of four 
genera and species of dinosaurs. Later, his descriptions were elab- 
orated and published‘ with illustrations. Although in his first 
article, Leidy thought that the Judith River formation might be 
of Wealden age, in his second publication he was inclined to con- 
sider the formation as “a part of the great Cretaceous series of 
Nebraska, though [he says] we should not feel surprised if future 
explorations should determine it to be of Tertiary age.’’> In the 
t Proc. Wash. Acad. Sci., XI (1909), 285. 
2 Stanton, op. cit., p. 286, refers to the widespread association of some of the species 
in association with the dinosaur fauna, stating that a “large proportion of them, 
including some of the more striking and characteristic forms, occur at Black Buttes.” 
3 Proc. Acad. Nat. Sci., Phila., VIII (1856), 72-73. 
4 Trans. Amer. Phil. Soc., XI, N.S., Philadelphia, 1860, pp. 138-54. 
5 Ibid., p. 140. 
