150 OSTEOLOGY. 
the attachment of the temporal fascia. Commencing in front at the external 
angular process of the frontal, the crest sweeps upwards and backwards across the 
lower part of that bone, and then crossing the coronal suture—a point called the 
stephanion—it passes on to the parietal, over which it curves in the direction of its 
posterior inferior angle. Here it is continued on to the temporal bone, where it 
sweeps forward to form the supramastoid crest, which serves to separate the squamous 
from the mastoid portion of the temporal bone externally. Carried forward, this 
ridge is seen to become continuous with the upper border of the zygomatic 
arch over the external auditory meatus. In front, the temporal ridge separates 
the temporal fossa from the region of the forehead; above and behind, it bounds 
the temporal fossa which lies within its curve, and serves to separate that hollow 
from the surface of the calvaria which is overlain by the scalp. Above the level 
of the temporal lines the surfaces of the frontal and parietal bones are smooth, 
the latter exhibiting an elevation of varying prominence and position, but usually 
situated about the centre of the bone, called the parietal eminence (tuber parietale). 
A slight hollowing of the surface of the parietal behind and parallel to the coronal 
suture is not uncommon, and is referred to as the post-coronal depression. As 
seen in profile, the part of the calvaria behind and below the lambdoid suture is 
formed by the tabular part of the occipital bone. In line with the zygomatic arch 
this outline is interrupted by the external occipital protuberance or inion (protuber- 
antia occipitalis externa). The projection of this point is variable; but its 
position can usually be easily determined in the living. Passing forwards from 
it, and blending anteriorly with the posterior border of the mastoid process of the 
temporal bone is a rough crest, the superior curved line (linea nuchv superior), a 
little above which there is often a much fainter line, the highest curved line (linea 
nuche suprema); this affords attachment to the epicranial aponeurosis. These two 
lines serve to separate the part of the cranium above, which is covered by scalp, 
from that below which serves for the attachment of the fleshy muscles of the back 
of the neck, the latter surface (planum nuchale) beg rough and irregular as 
contrasted with the smooth superior part (planum occipitale). The fulness of 
these two parts of the occipital bone varies much. There is frequently a pronounced 
bulging of the planum occipitale, and the position of the lambda can often be 
easily determined in the living; similarly the planum nuchale may be either com- 
paratively flat or else full and rounded. These differences are of course associated 
with corresponding differences in the development of the cerebral and cerebellar 
lobes which are lodged in relation to the internal aspect of these parts of the bone. 
The further description of the planum nuchale is best deferred till the base of 
the skull (norma basalis) is studied. 
Temporal Fossa.— Within the limits of the temporal lines the side of the cranium 
slopes forwards, inwards, and downwards, thus leaving a considerable interval between 
its lower part and the zygomatic arch. ‘This space or hollow is called the temporal 
fossa (fossa temporalis) ; bounded above and behind by the temporal lines, its inferior 
limit is defined by the level of the zygomatic arch. Deepest opposite the angle formed 
by the frontal and temporal processes of the malar bone, the fossa becomes shallow 
towards its circumference. Its floor, which is slightly concavo-convex from before 
backwards about mid-level, is formed above by the temporal surface (facies temporalis) 
of the frontal, behind by the anterior inferior angle (angulis sphenoidalis) of the 
parietal, as well as the lower portion of that bone, below the temporal crest ; below 
and‘in front by the temporal surface of the great wing of the sphenoid, and behind 
and below by the squamous portion of the temporal bone. Inferiorly the floor is 
limited in front by the free inferior border of the great wing of the sphenoid, which 
forms the upper boundary of the spheno-maxillary fissure; behind that, by a rough 
ridge, the infratemporal crest or pterygoid ridge (crista infratemporalis), which 
crosses the external surface of the great wing of the sphenoid, to become con- 
tinuous posteriorly with a ridge on the lower surface of the squamous temporal, 
from which the anterior root of the zygomatic process springs. In front the 
temporal fossa is separated from the orbit by the external angular process of the 
frontal above, and by the orbital process of the malar and its junction with the 
external border of the great wing of the sphenoid between the orbital and temporal 
