130 NATURE STUDIES. 



and we may conceive that this Compsognathus, tad 

 it been feathered, would have at least appeared to 

 resemble a bird much more nearly than a reptile. 

 But a still stronger piece of evidence in favour of 

 its bird-relationship awaits the naturalist when he 

 discovers that the hind limbs of these curious reptiles 

 are, in respect of structure, midway and between those 

 of birds and reptiles. If we examine the hind limb 

 of a bird (Fig. 5, A), we notice that the upper half of 

 the ankle ( A s, C a) unites with the shin-bone, or leg 

 (T) ; and as the lower half of the ankle joins the 

 instep (1), the ankle-joint thus exists in the middle of 

 the ankle-bones, and the lower ankle and instep-bones 

 form a single bone (m) by their union. In Fig. 2 the 

 hind limb of the bird is also seen, e being the single 

 bone formed by the union of ankle and instep-bones. 

 In the reptile's limb (C), the ankle-joint, as a rule, 

 opens between the divided ankle-bones; but the instep- 

 bones (C; i. ii. iii. iv.) are not united either to one 

 another, or to the neighbouring ankle-bones. Now it 

 is extremely interesting to discover that the hind 

 limb of Compsognathus and its allies (B) is exactly 

 intermediate between birds and reptiles. Here, the 

 leg bones resemble those of birds in shape. The 

 chief ankle-bone (A s) exactly corresponds with that 

 of a bird ; and, as in birds, this bone becomes united 

 to the lower end of the leg. But lastly, as if to show 

 the intermediate nature of the limb, the instep-bone 

 (I iv.) remains free, and the leg of Compsognathus is 

 thus practically halfway between that of the bird and 



