HADROSAURUS. 95 



As ill the case of the femur, in comparing the tibia of Iladrosaurus Avith that of 

 Cyclura, etc., we are struck with an apparent reversal of many of the anatomical 

 characters. Thus in the former the bone is longest externally, in the latter inter- 

 nally ; in Eadrosaurus the long diameters of the head and tarsal extremity are 

 opposed ; in Cyclura they are parallel. 



The fibula, represented in Figs. 7, 8, Plate XVI, from the left side, has lost its 

 upper fourth, and in its present condition measures twenty-eight inches in length. 

 At the broken extremity it is trilateral ; and it gradually expands in a flattened, 

 clavate manner to the lower extremity. Externally, Fig. 7, the bone is transversely 

 convex, and for the greater part of its extent internally is concave in the same 

 direction. The tarsal articular surface, Fig. 8, is bent ellipsoidal in outline, and 

 is convex and roughened. At the broken end the specimen measures one inch ten 

 lines in diameter ; the tarsal extremity is five inches and a quarter wide, and two 

 inches and one-third in thickness. 



The fibula of JHadrosaurus bears a near resemblance to that of Iguanodon, as 

 represented in Prof Owen's Figs. 3, 4, Plate XX, of the British FossU Reptiles, 

 Dinosauria. 



The two bones, represented in Figs. 7-10, Plate XIV, from their proportions are 

 supposed to belong to the metatarsus, and like the bones of the leg above described 

 probably appertain to the left side. 



The large specimen (Figs. 7, 8) has a cylindroid shaft, compressed from above 

 downwards and moderately expanding towards the extremities. The tarsal ex- 

 tremity is trilateral, flattened below, convex above, and presents a triangular con- 

 cave surface on its inner side. The tarsal articular surface is vertically crescentic 

 in outline and moderately concave. The phalangial extremity is quadrate, deeply 

 impressed sCt the sides for the attachment of lateral ligaments, convex above, and 

 deeply notched below. Its articular surface is vertically convex, slightly depressed 

 towards the middle inferiorly, and extends upon a pair of prominent condyles below. 

 The measurements of the bone are as follows: — 



Inches. Lines. 



Extreme length 12 8 



Length at its upper part . 11 3 



Breadth of shaft at middle ........ 3 3 



Depth of shaft at middle ........ 1 9 



Depth of tarsal extremity internally 4 6 



Breadth of tarsal extremity at middle ..... 3 4 



Height of phalangial extremity from a level ..... 4 2 



Breadth of phalangial extremity above and below .... 4 2 



The second specimen (Figs. 9, 10), suspected to belong" to the inner toe, has the 

 shaft cylindroid, but much compressed obliquely from within outwardly and above 

 downward. The extremities are broadly expanded and oblique in their position. 

 The tarsal extremity is more than twice the height of its breadth, and presents a 

 long elliptical articular surface, moderately concave at its upper two-thirds and 

 convex at its lower third. The phalangial extremity appears rhombohedral in out- 

 line with concave sides. Its articular surface is vertically convex and depressed 

 towards the median line. 



