616 VEKTEBRATA. 



Occipital, or Epencephalic ; 

 Parietal, or Mesencephalic ; 

 Frontal, or Prosencephalic 

 Nasal, or Bhinencephalic. 



(1650.) The OCCIPITAL YERTEBRA, in the higher vertebrates, is repre- 

 sented by the occipital bone, in which all the vertebral elements are 

 consolidated into one piece ; in the Beptilia, however, it is by no means 

 difficult to identify the several parts which enter into its composition. 

 They are as follows : 



Centrum Basioccipital .... 5* 



Neurapophyses . . . Exoccipital .... 9 



Spine Supraoccipital ... 8 



Pleurapophyses . . . Paroccipital . . . .10 



The composition of the PARIETAL VERTEBRA is 



Parietal centrum . . Basisphenoid . . . ^ , 6 

 Neurapophyses . . . Alisphenoid. 



Spine Parietal 7 



Pleurapophyses . . . Mastoid 12 



The FRONTAL YERTEBRA consists of 



, , f Prosphenoid and 



Frontal centrum . . 1 * 



[ Entosphenoid, 



Neurapophyses . . . Orbitosphenoid . . .14 



Spine Frontal 1 



Pleurapophyses . . . Postfrontal .... 4 



The NASAL YERTEBRA is composed of 



Nasal centrum . . . Yomer 16 



Neurapophyses . . . Prefrontal .... 2 

 Spine Nasal . . . .. / ' .. 20 



(1651.) Thus far we are enabled to identify the cranial bones as 

 being modified representatives of the spinal column, by allowing for 

 that increased development of the neural elements here rendered neces- 

 sary by the inordinate magnitude of the ganglionic centres of the cerebro- 

 spinal axis ; but when we come to turn our attention to the constitution 

 of the other portions of the chain, representing the lateral and inferior 

 arches, or, in other words, the parapophysial and the haemapophysial 

 elements, together with the diverging appendages derived therefrom, the 

 task becomes much more difficult. The labours of Professor Owen upon 

 this interesting subject, unparalleled for depth of research, and exhibit- 

 ing a grasp of philosophical argument rarely to be met with, have, how- 

 ever, satisfactorily revealed their real nature, and established beyond a 



* These numbers correspond with those that indicate the individual bones of the 

 cranium in subsequent figures. 



