]46 
EXTINCT YERTEBRATA FROM THE JUDITH RIVER 
CllOCODILUS HUMILIS. 
With the remains of Trachodon and Deinodon, Dr. Hayden discovered half a dozen 
teeth, apparently of a small species of Crocodile, though they may probably belong to an 
acrodont lacertian reptile. 
Five of the teeth, (figures 9—17, plate 11,) are conical and moderately curved; and on 
their inner part, in front and behind, they present the usual pair of acute ridges. About 
the middle of the crown, their enamelled surface is slightly folded, especially on the inner 
side of the teeth. They are solid, except that a small conical cavity occujhes the centre 
of their base. The latter is slightly concave and eroded in appearance; the borders only 
being broken, indicating that the teeth were about to be shed or actually were so, although 
most of them appear unworn. 
One of the specimens of teeth, (figures 18, 19,) is mammilliform, slightly compressed, 
and finely rugous in the length of the crown. It is likewise solid, and has the base pre¬ 
senting the same appearance as the other specimens. 
Explanation of Figures, Plate 11. 
Figures 9—19. Teeth of Crocodilus humilis, of the size of Nature. 
Figures 9, 10. Inner and lateral views of a conical tooth. 
Figure 11. Section of the same at base. 
Figures 12, 13. Inner and lateral views of another conical tooth. 
Figure 14. Section at base. 
Figures 15, 16, 17. Inner, lateral, and sectional views of a third tooth. 
Figures 18, 19. Outer and lateral views of a mammilliform tooth. 
PALiEOSCINCUS COSTATUS. 
In association with the remains of the great extinct saurians, Trachodon and Deinodon, 
Dr. Ilayden discovered the tooth of a true and gigantic representative of the family of 
Iguanians. The tooth is constructed on the same general plan as those of the existing 
Iguanas, consisting of a sub-palmate crown, with a compressed cylindrical fang. 
The crown of the fossil tooth, (figs. 49—52, plate 9,) is compressed pyramidal with the apex 
truncated, and is broader than long. Its base is elevated into a ridge; and from the sides, 
ridges extend to the free borders of the crown, where they end in points, some of which 
are acute and others are blunt. From the basal ridge of the crown, the tooth gradually 
narrows into a compressed cylindrical, hollow fang, the lower part of which, in the spe¬ 
cimen, is broken away. 
The breadth of the crown of the fossil tooth is 4 lines; its length from the basal ridge 
is 2i lines; and its thickness in the position of the latter, is 11 lines. The breadth of 
the fang at its broken end, is 2 lines; its width, 11 lines. 
