HADROSAURUS. 91 
The ulna, Fig. 5, Plate XIV, has a trihedral shaft becoming more cylindroid 
below, and has its three surfaces transversely concave above. ‘The olecranon is an 
irregularly rounded prominence. The coronoid process is a thick plate of bone 
gradually widening from the shaft upward antero-internally. A similar but smaller 
process, somewhat broken in the specimen, springs from the shaft externally. The 
brachial articular surface slopes in a concave manner from the olecranon downward 
and forward, and extends between and upon the two processes below. The lower 
extremity of the ulna slightly enlarges in its descent, is convex externally, forms a 
wide and rather deep groove internally, and ends in a convex carpal articular sur- 
face. 'The measurements of the bone are as follows :— 
Inches. Lines. 
Extreme length of the una. F j : , : : . 28 3 
Circumference at the middle of the shaft . : : - ; ag 
Greatest breadth at the coronoid process 5 
Greatest diameter of the carpal end 2 7 
Short diameter of the carpal end 2 
The interior of both bones of the forearm is occupied by a coarse spongy 
substance. 
The bones of the hinder extremities of Hadrosaurus are extraordinary for their 
huge size. In comparison with those of the fore extremities of the same animal 
they are of enormous proportions, exceeding in this respect not only all living 
Lacertians and Crocodiles, but even its extinct congener the /gwanodon. Thus in 
the Maidstone specimen of the Iguanodon, according to Prof. Owen,' the femur 
measures thirty-three inches long, while the humerus is nineteen inches; the tibia 
is thirty-one inches, and the ulna eighteen inches. In a collection of remains of 
the Iguanodon, from the Isle of Wight, according to Dr. Mantell,? the femur 
measured fifty-six inches in length, and the humerus thirty-eight inches. In 
Hadrosaurus the femur is forty-one inches and a half long, while the humerus is 
only twenty-two and a half, or little more than half the size of the former. The 
tibia is thirty-six inches and three-quarters long, and the ulna twenty-thtee inches 
and a quarter. 
The femur of Hadrosaurus, represented in Figs. 1-6, Plate XV, is of the left 
side. In general form and proportions it bears considerable resemblance to the 
corresponding bone of the Iguanodon, as represented by Dr. Mantell® and Prof. 
Owen.‘ It has a quadrilateral shaft, with the head and trochanter situated on the 
same line as the condyles. 
Extemally (Fig. 2) the shaft forms a nearly flat surface vertically and transversely, 
and is strongly marked at the upper part and just below the middle by muscular 
attachments. From the posterior surface the outer is defined by a convex, though 
somewhat interrupted, rising of the bone, which extends from the back part of the 
trochanter to the corresponding part of the external condyle. ‘The upper two- 
thirds of the outer surface are also defined in a similar manner from the anterior 
surface, but the lower third forms with the latter a more uniform convexity. 
1 British Fossil Reptiles, Dinosauria, p. 268. 2 Petrifactions and their Teachings, p. 801. 
5 Petrifactions, p. 292, Fig. 61. ‘ British Fossil Reptiles, Plate XX, Fig. 1. 
