1900.] SHUFELDT—OSTEOLOGY OF THE STRIGES. 685 
third cervical vertebra, most of its length being immediately 
beneath the prezygapophyses of each segnient. It is formed in 
the usual manner by the di- and parapophysial processes uniting 
laterally with the pleurapophysial elements. Small at the cephalic 
extremity of the column, its calibre gradually increases in each 
vertebra as we proceed toward the thoracic extremity, until it 
attains its maximum capacity at the eleventh vertebra. In the 
twelfth the integrity of its walls is lost by a parting of the par- 
and pleurapophysial elements, with a disappearance of the former, 
leaving it no floor, so that in this vertebra it ceases to be a closed 
canal. The most prominent object presenting itself for examina- 
tion in the atlas, superiorly, is the deep reniform cavity for articu- 
lation with the occipital condyle of the basi-cranii. Below and 
posteriorly there is another articulating surface, convex for the cen- 
trum of the axis and concave for its odontoid process, accurately 
meeting the opposed surface of this vertebra and forming the 
atlo-axoid articulation. A lip of bone, a portion of the hypa- 
pophysis of the vertebra we are now describing, projects 
downward and shields this joint in front, overlapping indeed 
a good part of the axis. The neurapophyses of the atlas 
are slight in structure. The concave postzygapophyses articulate 
with the convex prezygapophyses of the axis. The bone is 
devoid of a neural spine. In the axis we find both an hypapophysis 
and neural spine developed, the former being produced from the 
ridge on the anterior aspect of the centrum of the bone. The 
odontoid process arises vertically from the posterior margin of the 
upper surface of the centrum. Its summit and anterior face are 
convex and articulating, while behind it is flat and continuous with 
the spinal canal. The facet for articulation with the centrum of 
the third vertebra looks downward and inward, is convex from side 
to side and concave in the opposite direction. The postzyga- 
pophyses are concave, look downward and outward, the conditions 
in the prezygapophyses being exactly the opposite; this is the rule 
throughout the cervical portion of the column. After we pass the 
atlas and axis, we find in the third cervical vertebra here, as in 
most vertebrates, parts that are common to the series of this por- 
tion of the column, deviating but slightly from each other as we 
examine them 7% seriatim,; but gradually as this deviation pro- 
ceeds some requisite condition is brought about when the climax is 
attained. The fact of the presence of a neural spine on the axis is 
