EXTINCT ANIMALS 



the aperture for the spinal cord only 07ie large 

 condyle (marked Bas). From such a fragment 

 of the skull then you can at once tell whether 

 to place the creature to which it belonged 

 among the hairy warm-blooded quadrupeds 

 called mammals, or with the reptiles. A bird 



Fig. 47. — Photograi^h of tlie back of a Crocodile's skull to 

 show tlie single occipital condyle Bas, lying below the hole 

 or foramen by which the spinal cord enters the skull to 

 join the brain. 



is Uke a reptile in having a single joint or knob 

 at the back of the skull. 



As an example of the definite marks by which 

 bones can be referred to their proper classes, 

 the following is a curious point. Fig. 48 is 

 a drawing of the internal ear of man — the soft 



74 



