188 PRIMITIVE FORMS OF LIFE 



Apteryx. Their distribution seems to bear witness to their 

 antiquity, but a number of facts render this hypothesis doubtful. 

 We know from Archceopteryx, which has left fossil remains in 

 the Jurassic limestone of Solenhofen, that the ancestor of the 

 Birds preserved the long tail of the Reptiles ; that the jaws, 

 although invested with a horny plate, were not elongated into 

 a genuine beak, and that when this elongation took place it 

 did not at first cause the disappearance of the teeth with which 

 the jaws had been provided, since these occur also in the birds 

 of the Cretaceous Period, still inserted in separate alveolae, 

 in such forms as Archceopteryx, Ichthyornis, and Apatornis ; 

 or arranged in a common groove in Hesperomis, Enaliornis, 

 and Baptomis, which seems to presage their approaching 

 disappearance. It is scarcely probable that Archceopteryx 

 was capable of sustained flight. Its fore limbs were still 

 actually legs, whose four toes, provided with nails, were 

 definitely separated. The furcula was U-shaped, as in birds 

 of prey, but this form was not necessarily connected with flight. 

 In any case, the keel of the breast-bone was weak, and the long 

 tail, incapable of serving as a rudder, was rather in the nature 

 of a cumbersome ornament. Nevertheless, the feathers on 

 these anterior limbs and on the tail were already clearly 

 characteristic of the wing and tail feathers of flying birds, 

 so that they were actually prepared for flight. 



This faculty was well developed in Ichthyornis of the Chalk for- 

 mations, whose tail was already reduced to a rump and the keel of 

 whose breast-bone was very prominent. But Hesperomis, al- 

 though more highly evolved, could no longer fly, which is enough 

 to render suspect the antiquity of the loss of this faculty, and leads 

 us to ask whether we were correct in including in one order, 

 i.e. the Ratitse, all those large Birds without a keeled breast- 

 bone and incapable of flight. It is quite likely that the Ostriches 

 are the only members of this order which represent a primitive 

 group, by reason of their large wings, their almost normal 

 digits, and their united pubes ; but they represent a much 

 modified form, since their feet have but two toes. The Nandus, 

 with their large wings and their united ischia, would be typical 

 of a second group coming nearer to existing Birds. TEpyomis, 

 Dinornis, the Cassowaries, and Apteryx with open pelvis and 

 small wings — indeed, wings in miniature, for they are so con- 

 structed as to deserve in every respect the name of wings — 



