ANATOMY OF THE HORSE. 
149 
OCCIPITAL BONE. (oS OCCIPITIS.) 
Situation. Posterior and inferior part of the cranium. 
Figure. Symmetrical; irregular : presenting convexities and 
projections outwardly ; concavities, and a large circular aper¬ 
ture inwardly. 
Division. Into two surfaces, external and internal, and four 
borders. 
The External Surface is divided by a transverse mark'into two 
portions, a super-occipital and a sub-occipital portion, which 
were formerly two separate bones, and presents, Is^. along its 
median line, and from above downwards, the occipital crest, 
bounding the occiput posteriorly, and giving attachment to the 
complexus ; below this is the occipital tuberosity, to which is 
fixed the cervical ligament, with broad, rugged, posterior occipi¬ 
tal depressions marked by the attachments of the recti capitis 
postici; still lower is the occipital /m/^, transversely oval, and 
traversed by the spinal marrow and its membranes, the vertebral 
artery, and accessory and sub-occipital nerves ; below and in 
front of this hole is the basilar process, articulating with the 
sphenoid bone, whose under surface shews the basilar fissure, 
triangular and widening in its course to the occipital hole, where 
it terminates: to this process are attached the recti capitis an- 
tici. 2dly. On each side, the continuation of the crest, de¬ 
scending to the root of the styloid process of the same bone, 
into which is implanted the obliquus capitis superior ; below 
this, continued from it, is the styloid process, w^hose length is 
regulated by that of the jaws, affording attachment to the ob¬ 
liquus capitis anticus; inwardly to this, bordering on the occi¬ 
pital hole, are the occipital condyles, extending backw^ard for 
articulation with the atlas, and roughened upon their inner sides 
by the long odontoid ligaments; between the condyle and the 
styloid process is the condyloid notch ; and in front of the con¬ 
dyles, the condyloid foramina, which are , occasionally double, 
for transmitting the lingual nerves. 
The Internal or Cerebral Surface presents, superiorly, the occipi¬ 
tal cupola for covering the cerebellum, by which the surface is 
indented ; below, formed in the basilar process, the basilar fossa, 
wdiich supports the medulla oblongata upon its broadest and 
posterior part, the pons varolii upon its anterior and deeper 
part. 
Borders. The superior is denticulated and unites with the 
parietal bone ; the inferior or anterior, with the sphenoid ; the 
lateral borders join the petrous portions of the temporal bones. 
Development. In the foal this bone consists of four pieces ; 
