180 ON THE MORPHOLOGICAL CONSTITUTION OF 



petrosal, I quite agree with him. But while 1 do so, I make 

 a distinction between an ossified portion of the auditory 

 capsule and the bone which constitutes the corresponding 

 neurapophysis, in the same manner as I find myself compelled 

 to admit the independent existence of the ethmoidal neura- 

 pophysis and the olfactory capsules, whether fibrous, cartila- 

 ginous, or osseous, and the corresponding independent existence 

 of the variously-modified sclerotics and the orbito-sphenoids. 



Proceeding now to the examination of the remaining 

 elements of the post-stomal neural arches in the fish, I would 

 observe that if we put aside those conceptions of the constitution 

 of the arches in question, derived from previous study of the 

 cranium of the mammal, the constitution of the corresponding 

 arches in the fish which naturally suggests itself is the 

 following : — 



1. Over the occipital centrum the lateral occipitals and the 

 external occipitals — as two pairs of neurapophyses, and the 

 superior occipital — as a single meta-neurapophysis. 



2. Over the position of the temporal centrum, the bones 

 termed petrosals by the continental anatomists, but by Professor 

 Owen petrosals in the cod, and ali-sphenoids in the carp, and 

 over these the mastoids, these " petrosals " or " ali-sphenoids," 

 along with the mastoids — as two pairs of neurapophyses, and 

 the contiguous or separated bones usually termed " parietals," 

 as a divided meta-neurapophysis. 



3. Over the great basi-sphenoid, the bones termed by 

 Professor Owen orbito-sphenoids in the carp, and ali-sphenoids 

 in the cod, with the post-frontals — as two pairs of neurapo- 

 physes, the meta-neurapophyses being absent. 



Before making any statements in support of this view of 

 the constitution of the post-stomal neural arches in the 

 cranium of the osseous fish, I would direct attention- to the 

 corresponding parts in the other Vertebrata from the same 

 point of view. 



