228 ELEMENTARY ANATOMY. [LESS. 



the olfactory and auditory organs, is protected by bony ex- 

 pansions (the bony orbit) round it. 



Beneath the basis cranii we have (i) the great cornua 

 of the hyoid, which send up no connecting ligaments to it, 

 but which through the basi-hyal are connected, by the lesser 

 cornua, with the styloid processes. (2) In front of this 

 hyoidean arch we have the mandibular arch, and (3), again 

 in front of this, the arch of the upper jaw, ending posteriorly 

 in the pterygoid bones and amalgamated in front with the 

 osseous covering of the nostrils (the nasals) and -with the 

 outer protection of the orbits (the malars), which latter send 

 back a bony arch (the zygoma) to the bony envelope of the 

 auditory organ. 



15. If we descend greatly in the Vertebrate scale as, for 

 example, to an osseous Fish we find the same generalized de- 

 scription will apply, while the cornua and the cornicula of the 

 hyoid are more solidly represented, and similar serial homo- 

 logues are developed in succession behind them. A lateral 

 zygoma (like that of man) is wanting in the Fish, but interme- 

 diate forms (e.g. the Crocodiles and Sphenodori] have shown 

 us that there may be two lateral bony arches extending back- 

 wards, one above and one below the orbit, and separate one 

 from the other. A striking difference from man may be pre- 

 sented by the ossification around the internal ear in Fishes, 

 \rhere, instead of being in one bony piece, hardly visible but 

 at the base of the skull, it may be in five distinct pieces, visible 

 at the back and the roof of the skull, and forming a very large 

 part of its side wall. Many other differences also exist, the 

 more important of which have been noted in Lesson III. 



As has been said more in detail in that Lesson, the 

 bones of the face, including the jaws and hyoidean and 

 branchial arches, are all ossifications in and about the carti- 

 laginous arcs of the several visceral arches, or splanchnapo- 

 physes. 



1 6. Since the facial parts may be reckoned to be splanchna- 

 pophysial, and therefore, as we have seen, more or less related 

 to the hypapophyses of the trunk (because hypaxial in their 

 nature), it remains for us to consider what are the most general 

 relations of the cranial (as distinguished from facial) parts 

 of man and of other Vertebrates to what category of spinal 

 axial parts may they be said to appertain ? 



As the side walls of the cranium are developed in the 

 laminae dorsales, and in part invest the notochord, they 

 must be reckoned to be essentially epaxial parts ; but are 



