CRANIAL CHARACTERS OF THE SNAKE- RAT. 69 



The circumstance which gives especial weight to this difference 

 in the occipital foramina of the two skulls is that it involves a 

 corresponding difference in the large nervous centre (the medulla 

 oblongata) which occupies the foramen. I conceive that osteal 

 characters or forms associated with corresponding modifications of 

 any portion of the nervous system are of first-class importance. 

 This would especially apply, in the case I am considering, to the 

 foramen magnum occipitale : the same principle would hold good, 

 in a minor degree, as to the differences already mentioned in the 

 infra-orbital foramina, which transmit the nerves distributed to 

 the tactile organs about the mouth. 



Fig. 5. Fig. 6. 



Under view of Cranium of Snake- Under view of Cranium of Mas 



Eat, minus the lower jaw. En- rattus, minus the lower jaw. 



larged two diameters. Enlarged two diameters 



On the under surface of the skulls there are further distinctive 

 differences. In the new rat the foramen ovale is hid by the lateral 

 spreading of the pterygoid processes of the sphenoid bone ; in the 

 Black Eat it is exposed. The breadth of the palate, the size of 



