OSTEOLOGY 31 



the cranium superior to the ala sphenoida temporale. It extends 

 outward and anteriorly over the rims of the petrosum and 'ala 

 sphenoida orbitale. The squamous part forms the upper three- 

 fourths of the cochlea, the inner auditory canal, the upper partTrf 

 the fenestra ovalis, the anterior vertical and the outer semicircular 

 canal, and the lower part of the posterior vertical semicircular canal. 



The petrous portion forms the posterior wall of the foramen 

 ovale and the fenestra ovalis in which lies the columella. The 

 fenestra ovalis and the fenestra rotunda are the only two entrances 

 into the labyrinth. In this region may be seen the fusion line 

 between the os petrosum and the os occipitale. Superiorly and 

 posteriorly the petrous portion touches the external parietalia 

 and occipitalis; infero-laterally it unites with the basi-sphenoid. 

 The outer rim of the foramen ovale is broadened by the ala sphen- 

 oida and mesially by the basi-sphenoid. This foramen gives exit 

 to the second and third divisions of the fifth pair of cranial nerves. 



The lateral surface of the temporal bone presents a short tube, 

 the external acoustic process, or processus acusticus externus, to 

 which is attached the concha of the ea.r. The process is directed 

 outward. Its lumen, the external acoustic meatus, or meatus acus- 

 ticus externus, conducts to the cavity of the middle ear in the bare 

 skull, but is separated from it by the tympanic membrane in the 

 natural state. 



BONES OF THE FACE 



The bones of the face, or ossa faciei, are the premaxillary, or 

 upper mandible, the maxillae, the nasal, the lacrimal, the palatine, 

 the pterygoid, the zygomatic, the vomeral, the jugal and the 

 quadrato-jugal. The vomer is single, the others are paired. In the 

 inferior maxillary group there are the quadrati, and the inferior 

 maxillary, or lower mandible. The turbinated and hyoid bones 

 are also discussed with the bones of the face. 



The beak consists of the anterior portion of the upper and lower 

 mandibles which are covered with a horny structure. 



The Premaxilla. Location. The premaxillse, or ossa incisiva, 

 or mandibular structures, are located in the extreme anterior 

 facial region. 



Description. The premaxillae are long and the anterior end 

 is pointed. Each consist of two lateral halves which become fused 

 before the chick is hatched. They partly circumscribe the openings 



