NATURAL SCIENCES OF PHILADELPHIA. 
217 
inches in circumference at the middle. The radius is 20 inches long, and 6 
inches in circumference at the middle. 
A very great disproportion exists between the bones of the fore and hinder 
extremities. So much is this the case, that I was at first inclined to believe 
thej belonged to different animals. The disproportion is even greater than in 
the Iguanodon, as indicated by comparison with the remains of an individual of 
the latter, in the British Museum, known as the Maidstone specimen. 
The ilium has its two extremities broken away, and in its present condition is 
27 inches long. Its sacral articular surface is 12 inches long by 3 inches thick. 
The breadth of the bone, opposite the latter surface, is from 7 to 9 inches. A 
bone, which I suspect to be the pubic, but whicU appears to correspond with 
that, of the Maidstone Iguanodon, described as the clavicle, is 26 inches long in 
its present state ; one end being broken away. The remaining pubic extremity is 
lOJ inches wide. 
The thigh bone is 40 inches long ; its breadth at the head and adjoining tro- 
chanter is 9 inches ; its breadth at the condyles is 8 inches ; and the antero-pos- 
terior diameter of the internal condyle is 10 inches. The shaft is quadrate, and 
provided at its middle portion internally with a large trochanter. The cir- 
cumference of the shaft just above the latter is 17 inches ; just below it, 15 inches. 
The condyles in front enclose a large foramen terminating a groove descending 
from the shaft. Posteriorly, at the bottom of the intervening notch, they enclose 
a smaller foramen. The medullary cavity is of large size, and extends about 
half the length of the shaft through its middle portion. 
The tibia is 36} inches long ; its breadth at the upper part is 11 inches ; and 
its breadth below is 10 inches. Its shaft is narrow and cylindroid at the middle, 
where it measures 11| inches in circumference. From this position it rapidly 
expands towards the two extremities of the bone. The medullary cavity is very 
short and narrow. 
The two metatarsal bones are of robust proportions and are each about 11 inches 
long. The proximal jyhalajix of a toe is 6 inches long, and 5|: inches broad at 
base. 
If we estimate the number of vertebrae of the trunk of Hadrosaurus to have 
been the same as in the recent Crocodile and Iguana ; the number of sacral ver- 
tebrae to have been the same as in the Iguanodon ; and the number of caudal 
vertebrae to have been fifty ; the whole number of vertebrae would have been 
eighty. A calculation of the length of the specimens of vertebrae in our posses- 
sion, with a proper allowance of separation by intervertebral fibro-cartilages, 
and an addition of two and a half feet as an estimate of the length of the head, 
would give, as the total length of the animal, about twenty-five feet. 
The great disproportion of size between the fore and back parts of the skeleton 
of Hadrosaurus, leads me to suspect that this great extinct herbivorous lizard 
may have been in the habit of browsing, sustaining itself, kangaroo-like, in an 
erect position on its back extremities and tail. As we, however, frequently ob- 
serve a great disproportion between the corresponding parts of the body of re- 
cent and well known extinct saurians, without any tendency to assume such 
a position as that mentioned, it is not improbable that Hadrosaurus retained the 
ordinary prostrate condition, progressing in the manner which has been sus- 
pected to have been the case in the extinct batrachian of an earlier period, the 
Labgrinthodoti. 
Hadrosaurus was most probably amphibious ; and though its remains were 
obtained from a marine deposit, the rarity of them in the latter leads us to sup- 
pose that those in our possession had been carried down the current of a river, 
upon whose banks the animal lived. 
Occasionally uncharacteristic fragments of huge bones have been found in 
the green sand of New Jersey, (of which we have several in the collection of 
the Academy,) which I suspect to belong to Hadrosaurus. One of these speci- 
mens, exposed to the view of the members, indicates a much larger individual 
than the one whose remains have been presented this evening. 
1858.] 
