GIANT LAND REPTILES OR DINOSAURS. 129 



action of walking, it is evident that the joint is situated 

 between the two long-bones of the leg and the upper 

 row of the ankle, i.e., the heel-bone and huckle- 

 bone. In a crocodile, on the contrary, the ankle joint 

 occurs between the upper and the lower rows of the 

 ankle, so that the heel-bone and the huckle-bone move 

 with the leg-bones. In a bird there is yet one step 

 further on this, for not only does the movable joint 

 occur between the upper and the lower rows of the 

 ankle, but the huckle-bone and the heel-bone are 

 respectively united with the two long-bones of the 

 leg, so as to form practically single bones ; while the 

 bones of the lower row of the ankle similarly unite 

 with the long-bones supporting the toes, so as to form 

 that single slender bone, with three pulley-like lower 

 surfaces, with which we are all familiar in the leg of a 

 fowl (see Fig. 47, B, p. 151). An adult bird, therefore, 

 while having an ankle-joint, has no separate ankle- 

 bones. In a young bird, however, as we may see for 

 ourselves in the case of a young fowl on our dinner- 

 table, the lower end of the so-called " drumstick," or 

 main bone of the leg, is incompletely united to the bone 

 itself, so that it can be readily detached ; this detachable 

 portion being, in fact, the bird's true huckle-bone. 



Now in the crocodile, as we have already mentioned, 

 the huckle-bone, although moving with the leg-bone, 

 remains perfectly separate therefrom; but in the 

 Megalosaur we find a condition exactly intermediate 

 between that obtaining in the crocodile and the adult 

 bird. This will be apparent from Fig. 38, where we 



