AND GREAT LIGNITE FORMATIONS OF NEBRASKA. 149 
In association with the remains of several other genera of Turtles, and of some other 
animals in the Great Lignite Tertiary Basin, near Long Lake, below Fort Clark, Nebraska, 
Dr. Hayden obtained small fragments of the carapace or osseous shell of a Turtle, not dis- 
tinguishable from those referred to, Trionyx foveatus. The specimens are too imperfect 
positively to determine whether they actually belong to the same species. Fragments of 
a last costal plate, represented in figure 5, plate 11, measures 4 lines in thickness, and are 
closely foveated on the exterior surface, in the manner described in the account of the cor- 
responding plates of 7’rionyx foveatus from the Judith River. 
Explanation of Figures, Plate 11. 
Figures 1—3. Fragments of the carapace and sternum of TRIONYX FOVEATUS, of the natural size. 
Figure 1. Two fragments of a hyposternal plate; an ideal outline given in the restored condition. 
Figure 2. Fragment of a left costal plate. 
Figure 3. Fragment of the last right costal plate, supposed to belong to the same species as the preceding. 
FISHES. 
LEPIDOTUS OCCIDENTALIS. 
The genus of ganoid fishes Lepidotus, appears to have come into existence during the 
Liassic period, to have extended through the Oolitic, Wealdean, and Cretaceous periods, 
and to have become extinct in the Eocene Tertiary period. 
As if to keep up the association, in the manner that Dr. Mantell found together in the 
Wealdean deposits the remains of Igwanodon, Megalosaurus, Crocodilus, and Lepidotus, Dr. 
Hayden discovered with the remains of Vrachodon, Deinodon, and Crocodilus, a half dozen 
ganoid fish scales, which appear to belong to the genus Lepidotus. The specimens may 
indicate two species, but with equal probability they may appertain to a single one. 
Four of the scales, (as represented in figures 20, 21, plate 11,) are lozenge-shaped, with 
their root prolonged from one side in the direction of the longest diameter of the lozenge. 
Two of the scales, (as represented in figures 22, 23,) are square, with their root projecting 
from one of the longer sides. All the specimens are invested with thick, shining, enamelled 
substance; and one of the square scales exhibits on its free surface, parallél square lines of 
growth. 
The largest lozenge-like scale has the sides of its free or enamel surface about 4 lines 
long; and the smallest has two of the sides 3 lines long, the other sides 2 lines long. The 
larger square scale has its long sides 5 lines, and its short sides 54 lines. 
Explanation of Figures, Plate 11. 
Figures 20—23. Scales of Leprporus OccIDENTALIS, of the natural size. 
VOL. xI.—20 
