THE SKELETON OK THE VEUTEbUATK HEAD. 183 



occupied Ity tibiuus texture; the "basi-spheuoid" or post- 

 splieuuidid centrum extending forwards below ; and the " pari- 

 etals" taking the place of the deficient meta-neurapophyses. 



The preceding view of the arrangement of the centrums 

 and neunil arches of the post-stomal sclerotomes of the lower 

 forms of cmniiim, is that which would appear naturally to 

 suggest itself to a muid uninlhienced by the arrangement of 

 the corresponding region of the niammalian skulL It is 

 assumed throughout that there are more or less complete carti- 

 laginous or osseous auditory capsules in addition to correspond- 

 ing neumpophyses ; and that these neurapo]»hyses are not 

 post-sphenoidal but temporal, as evinced by their zygopophy- 

 seal connections in the human craniimi. No reference has 

 been made to the relations of the contested " petrosals" and 

 ali-sphenoids" to the fifth nerve, because, while the fimda- 

 mental relation of that nerve to the post-sphenoidal sclerotome 

 is admitted, the divisions of the nerve exhibit the same 

 tendency to vary in their points of exit, as is presented by the 

 other cerebral nerves ; moving backwards more or less across 

 the corresponding neurapophyses, and notching or perforating 

 the neurapophyses behind. In fact, until a more minute 

 investigation of the development of the cranium in its relations 

 to the cerebral nerves has afforded some ex})la)iation of the 

 varied relations of these parts in the series, we cannot, in 

 my opinion, attach much weight to the deterndnation of a 

 " petrosal" or an " uli-sphenoid" by means of their relations 

 to the trigeminal nerve. 



Proceeding now to the examination of the post-stumal 

 centrums and neural arches of the mammalian cranium, let 

 the human skull be selected for examination. The occipital 

 centrum is surmounted by a pair of ncuraiKtphyses and a 

 double meta-neuiiipophysis. lUit again, surmounting the 

 meta-neurapophyses there is a double piece, which occasion- 

 ally remains permanently sc'j)arat<' from the " occipital Itone." 



