HADROSAURUS. 93 
the condyles. Posteriorly the latter are separated by a deep, wide notch. A deep 
popliteal concavity (Fig. 4, g) communicates below with a short, wide canal (Fig. 
6, g) perforating the conjunction of the condyles posteriorly. A similar perforation 
exists in the recent Cyclura. 
The posterior projection of the outer condyle is broken off in the specimen; that 
of the inner condyle exhibits a large rugged surface (Fig. 4, d) for the gastrocnemial 
attachment. The external condyle projects rather more inferiorly than the internal, 
but appears not to have been so extensive in its antero-posterior diameter. 
The interior of the bone exhibits a capacious medullary cavity. 
The measurements of the bone are as follows :— 
Inches. Lines. 
Length of the femur from top of trochanter to bottom of external 
condyle . oe: Riff . 41 6 
Length from top of head . bottom of triers ehandgld : é 39 
Breadth of upper extremity : ; : : . 5 ; eee) 3 
Breadth of lower extremity ; : : é : : i 38 5 
Transverse diameter at middle of shaft > : - : A Eeeiy 2 
Antero-posterior diameter at middle of shaft  . : ; : ea 6 
Circumference below middle trochanteroid process. : : 2) wl 
Circumference above middle trochanteroid process. 2 : LY 
Antero-posterior diameter of head. ‘att : c : pe: 8 
Antero-posterior diameter of trochanter. - , , : Sal 9 
Antero-posterior diameter of inner condyle - - : : SUD 
In comparing the femur of Hadrosaurus with that of the living Cyclura and 
Iguana, to which it bears a nearer resemblance than to that of the Crocodiles, it 
would appear as if the condition of most of the anatomical characters were either 
reversed or their meaning had been mistaken. Thus in Hadrosaurus we have 
described the head of the femur as being internal and the trochanter external. In 
Cyclura and Iguana the head of the bone is external and the trochanter postero- 
internal. In Hadrosaurus the head is slightly below the level of the trochanter ; 
in Cyclura it is considerably higher. In Hadrosaurus the shape of the trochanter 
is nearly like that of the head in Cyclura, and is nearly as large as the head of the 
same bone, but in Cyclura it is much smaller. In the former the femur is longest 
from the trochanter to the external condyle; in the latter from the head to the 
external condyle. Lastly, in Hadrosaurus the internal condyle is the larger; in 
Cyclura the external is the larger. 
The tibia of Hadrosawrus, represented in Figs. 1-6, Plate XVI, is of the left 
side. It approaches in form and details of structure that of the Jywanodon, as 
represented in Prof. Owen’s Fig. 2, Plate XX, of the British Fossil Reptiles, Dino- 
sauria. It is, however, proportionately more slender towards the middle of the 
shaft, and it appears twisted in such a manner that the broad extremities cross 
each other in the direction of their greatest diameter, whereas in Jyuwanodon the 
broad extremities are nearly on the same plane. 
The tibia is about three feet in length, and is cylindroid at the middle of the 
shaft, which rapidly expands into broad, clavate extremities. 
The fore part of the shaft, Fig. 1, is nearly straight vertically, is smooth, and 
widest at its upper part. For the greater part of its extent it is transversely con- 
