AND GREAT LIGNITE FORMATIONS OF NEBRASKA. 143 
The length of this specimen, on the outer side, as represented in figure 20, is 53 lines; 
the breadth, 4 lines; the width at base, 4% lines. 
Another specimen consists of the longitudinal fragment of a tooth, as represented in 
fieure 16. The triturating surface, (figure 17,) is level and smooth, and corresponds 
with the transverse section of the fragment. ‘This section is quadrate, with one of the 
sides formed by the broken border of the tooth. The other sides are concave, with the 
intervening angles prolonged; one of them being bevelled, and the other doubly so. The 
base of the fragment is enveloped in a thick, rugged osseous layer. 
Explanation of Figures, Plate 9. 
Figures 1—20, Teeth of TRACHODON MIRABILIS. 
Figures 1—6, of the size of Nature. 
Figures 7—20, magnified two diameters. 
Figure 1. Inner view of an inferior tooth, exhibiting the lozenge-shaped enamel surface divided by a median 
carina. The form of the fang restored in outline. 
Figure 2. Lateral view of the same specimen, exhibiting the roughened outer surface, and at @ a portion of the 
surface impressed by the crown of a lateral successor. 
Ficure 8. Outer view of the same specimen. 
Vigure 4. Section of the crown at the position marked 0, fig. 1. 
Figure 5. Section at the position marked c, fig. 1. 
Fieure 6. Section at the broken extremity d, fig. 3. 
Figure 7. Remains of a much worn tooth, apparently from the upper jaw, external view. 
Figure 8. Internal view of the same specimen, exhibiting at e the hollowed base. 
Figure 9. Triturating surface of the same specimen, exhibiting the crucial ridge of harder dentinal substance. 
Figures 10, 11, 12. Similar views to those last indicated, of another tooth. 
Figures 18, 14, 15. Similar views of a third tooth. 
‘Figure 16. Outer view of the remainder of a much worn tooth; the base enveloped by a thick osseous crust: 
Fieure 17. Triturating surface of the same specimen. 
Figure 18. A slightly worn tooth, of peculiar form; apparent inner view. 
Figure 19. Lateral view of the same specimen. 
Figure 20. Outer view. 
DEINODON HORRIDUS. 
In association with the remains of the huge herbivorous Jguanodon, Dr. Mantell found 
remains of a fit carnivorous cotemporary, the Megalosaurus. This great saurian, named 
by Dr. Buckland, and first discovered by him in the Oolitic Formation of England, pos- 
sessed sabre-shaped teeth, with trenchant serrated edges, over three inches in length and 
an inch in breadth, supported in the jaws by an outer parapet: wall, and passing one an 
other like the blades of scissors. 
