PEDIGREES — THE FOUNDERS OF THE HOUSE. 233 



such alterations, and retains something like the 

 original five-fingered form from which it started. 



The bird then we have agreed is of reptilian 

 origin, and of the reptiles resembles most nearly 

 the dinosauria. Most nearly — this implies that 

 it has also characters wherein it resembles other 

 reptiles ; and so it has. Of these we will now 

 select a few examples. 



Let us take the skull. In this, in many 

 reptiles, we find true teeth. These are either 

 implanted in the jaws in grooves or in sockets. 

 In the earliest birds — Archceopteryx, HesperorniSy 

 and Ichthyornis — we have also teeth in the jaws. 

 This would suggest that the birds come from 

 a reptilian stock possessing teeth. They were 

 implanted in sockets in Arclimopteryx and Ich- 

 thyornis, and grooves in Hesperornis. The 

 pterodactyles had teeth, but some of the more 

 specialised amongst them exchanged these for 

 horn-encased jaws like those of our modern 

 birds. 



The skull, in all existing reptiles and birds, 

 is joined to the vertebral column by a single 

 rounded knob called a condyle. In the class 

 next below the reptiles, to which the frogs and 

 toads belong, and in the class next above the 

 birds, the mammals, the skull joins on to, or 

 articulates with, the vertebral column by two 

 condyles, arranged pairwise instead of a single 

 median one. But besides these we find in the 

 skull numerous other points shared in common 

 between the bird and reptile which are of too 

 technical a nature to be dealt with here. 



Birds and some reptiles, but no other animals, 



