THE EVIDENCE FROM MISSING LINKS. 



157 



and their haunch-bones are united below or in front, instead of 



remaining open as in other birds. But he would be worse than an 



over-bold zoologist who would venture to maintain 



that such points of difference meant more than the 



merest tendency reptilewards ; and the ostriches and 



their neighbours can hardly be denominated links 



which appreciably narrow the gulf betwixt reptiles 



and their bird kith and kin. But presuming that the 



zoologist, dealing with the birds of to-day, refuses / 



assent to the idea that he can supply us with missing 



links between reptiles and birds, can the contents of 



the geologist's aviary be shown to be better adapted 



to supply the gap ? Research here may proceed in 



two directions. Either we may try to discover if any 



extinct birds are nearer reptiles than their living 



allies ; or, we may endeavour to ascertain if any fossil FIG. 77. LEG AND 



reptiles exhibit a closer relationship with birds than A ^'^ fuiwr^ wn 



the reptiles of to-day. We may very profitably dis- biVd ; B, in the young 



cuss, in brief detail, both aspects of the case. 



Fossil birds make their first appearance in the Upper Oolite 



FIG. 78. FIG. 79. 



FOSSIL FOOTPRINTS FROM TRIASSIC ROCKS. 



rocks formations lying in their natural order just below the chalk. 



