HADROSATJRUS. 91 



The iilna, 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 : — 



Inclies. Lines. 



Extreme length of the uTna 23 3 



Circumference at the middle of the shaft ...... 7 



Greatest breadth at the coronoid process 5 



Greatest diameter of the carpal end 2 t 



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 Hadrosaihrihs 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 Iguanodon. Thus in 

 the Maidstone specimen of the Iguanodon, according to Prof. Owen,^ the femur 

 measures thirty-three inches long, whUe 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-three inches 

 and a quarter. 



The femur of Hadrosaurus, represented in Pigs. 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. MantelP and Prof. 

 Owen.* It has a quadrilateral shaft, with the head and trochanter situated on the 

 same line as the condyles. 



Externally (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 vuiiform convexity. 



* British Fossil Reptiles, Dinosauria, p. 268. " Petrifactions and their Teachings, p. 301. 



= Petrifactions, p. 292, Fig. 61. * British Fossil Reptiles, Plate XX, Fig. 1. 



