216 
PROCEEDINGS OF THE ACADEMY OF 
are provided with short, transverse, tuberculated ridges. The body of the 
crown outwardly is paraboloid in transverse section, and is prolonged into a 
laterally compressed conoidal fang. As the teeth were worn away from the 
summit, their gradually expanding triturating surface sloped downward and 
outward. This surface is shield-like in outline, is bordered by enamel in- 
ternally, and crossed by a slightly elevated crucial ridge with diverging 
branchlets. The ridge, resulting from the later ossification of the dental pulp, 
is harder than the surrounding dentine, and is adapted to retain a rough tri- 
turating surface. The sides and bottoms of the teeth exhibit the impres- 
sions of lateral and inferior successors, and appear to indicate that the teeth 
in use, together with those more or less developed within the jaw, had a quin- 
cuncial arrangement. 
Two of the specimens of teeth perhaps belong to the upper jaw. They differ 
from the others in the extraordinary degree of development of the median 
carina of the crown. The enamelled surface was perhaps directed in a re- 
verse manner to that of the lower teeth; that is to say, outwardly. It is like- 
wise lozenge-like in outline, and tuberculated at the lower borders. The body 
of the crown inwardly is half oval in section. The fang for more than half its 
width is prolonged from the carina of the crown. These teeth also exhibit 
the impress of successors holding the same relative position with one another 
as in the lower teeth. 
The fragment of the lower jaw is a portion of the left dentary bone, and is 
three inches in depth. It has an outer parapet wall about two inches high, 
with deep vertical grooves for the support of ihe teeth. No corresponding wall 
appears to have existed on the inner side of the latter. 
The cervical vertebrae have their bodies prominently convex in front and 
deeply concave behind, and would appear to indicate that Mantell was correct 
in assigning similar vertebrae, found in the Wealden deposits of England, to the 
Iguanodon. Tbree cervical vertebras, suspected to be the third, fourth, and 
fifth, are two and a half inches long at the sides. 
Five succeeding vertebrie, not immediately conjoining the ones just men- 
tioned, and supposed to be anterior dorsals, likewise have convexo-con- 
cave bodies. At the sides of the latter they are from 3 to 3|- inches long, and 
posteriorly are 3^ inches wide. The sides of their arch present a deep pit for 
the articulation of a rib ; but no articular mark is perceptible at the sides of 
the bodies. Two other vertebrae, perhaps posterior dorsals, have the bodies 
slightly prominent in front and slightly concave behind; and they are 3 J inches 
long at the sides, and 4| inches wide posteriorly. 
The caudal vertebrae possess articular surfaces for chevron bones ; and the 
specimens we possess, from diff'erent parts of the tail, give the following suc- 
cession of measurements of their bodies : length 2|- inches, breadth 5 inches ; 
length 3 inches, breadth 4i inches; length 3 inches, breadth 3 J inches; 
length 2| inches, breadth 2\ inches; length 2-J inches, breadth If inches. 
From the gradation of size of seventeen specimens in the collection, it may 
be estimated that there were originally about fifty vertebrae to the tail. This 
number maj^ be too great by about ten, but certainly not more. 
A caudal vertebra from near the middle of the tail has its arch and spinous 
process complete. The two latter together measure 11 inches long from the 
body, which is 4J inches deep. The addition of a chevron bone would indicate 
the tail of the animal, at its middle, to have been between one and a half 
and two feet in depth. 
The humerus is perfect, and is 23 inches long. Its breadth at the tuberosi- 
ties, between which the head projects midway, is 7 inches. The shaft above 
is compressed from without inwardly; its lower part is cylindroid, and near 
the middle of the bone measures 9| inches in circumference. At the condyles 
the transverse diameter is 5^ inches. Only a very short and narrow medullary 
cavity occupies the centre of the shaft. 
Both bones of the forearm are solid. The ulna is 23 inches long, and 7 
[Dec. 
