286 TOWARDS THE HUMAN FORM 



which they are more backward than the Orthopod Dinosauridse. 

 They have, however, lost three of the toes of their feet, showing 

 that the type had already experienced important modifications. 

 They are present in the Miocene of Samos. 



The Nandus also lived in the Miocene, but in South America. 

 As in the ostriches, the pelvis was closed, though in their 

 case by union of the ischia, whereas it was the pubic bones 

 that were united in the ostrich : the foot terminated in three 

 toes, the wing digits had already the conformation found in 

 flying birds, and they were still further removed from the 

 ostriches by the structure and position of the vocal organ 

 or syrinx. It is probable that they did not even belong 

 to the same series. 



The Cassowary group is represented in the Pliocene by 

 the genus Hypselornis. These birds have scarcely any wings, 

 but the skeleton of this minute wing with its two united 

 digits is that of degenerate Birds which have lost the ability 

 tony. 



After the Ratites, the present-day birds presenting the most 

 primitive characters are the Tinamous of tropical America. 

 They are characterized by the union of the vomer with the 

 palatine bone, a condition already indicated in the Emu and 

 Apteryx, by the articulation of the quadrate with the skull 

 by a single condyle, the absence of union in the ilium and 

 ischium, and the independence of all the caudal vertebrae. 

 But they are not known in the fossil state. In the Miocene 

 we find every type of Bird already represented, as the fine 

 work of Alphonse Milne Edwards on the fauna of Saint-Gerand- 

 le-Puy in the department of the Allier have shown. Nothing 

 enlightens us as to their past, so that interest becomes con- 

 centrated on Mammals, whose wonderful and gradual expansion 

 during the Tertiary Period constitutes one of the most brilliant 

 chapters of Natural History. 



Mammals had lived side by side with Reptiles from Triassic 

 times, but during four million years they occupied a modest 

 position, effaced by their small size. As with Birds, they only 

 became important when the day of the Reptiles was over, 

 but their progress, instead of being made in regard to detail, 

 fundamentally modified their organization and was slower 

 than that of the Birds. Accordingly, we can follow it step 

 by step. We must not imagine, however, that this evolution 



