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tract of bone, arching down between the occipital and temporal regions to be- 

 hind the base of the zygoma, and terminating below in the rugged apophysis 

 supporting the stylo-hyal articulation. This arched tract bounds by its poste- 

 rior ridge the occipital region, and by its anterior one, the temporal fossa ; but 

 its lower half is separated from the occipital region by a broad and deep vertical 

 excavation, which has lodged the origin of the digastric muscle. 



The anterior ridge arches forwards superiorly, and is continued above the 

 long temporal fossa to the external angular boundary of the orbit : below, the 

 same ridge is continued upon the upper and outer angle of the zj^goma. The 

 temporal depression is twice as long as it is deep ; its length more than equals 

 half that of the entire cranium : it is not separated from the orbit, but the re- 

 spective limits of these cavities are indicated by the slight angular process 

 above noticed. The surface of the temporal depression is roughened by small 

 reticularly decussating ridges of bone, which fall towards the lower outlet into a 

 sloping direction, corresponding with that of the fasciculi of the temporal 

 muscles as they converged to their insertion into the broad coronoid process 

 of the lower jaw, which here enters the temporal fossa. A slight horizontal 

 depression along the middle of the posterior part of the temporal fossa indicates 

 the upper margin of the squamous bone. 



The zygomatic process of the temporal bone is a strong, nearly straight, tri- 

 hedral process, extending forwards and outwards, and with the extremity inclined 

 upwards. Its external surface is nearly flat, and is continued from the anterior 

 part of the tympanic cavity : the angle separating the external from the internal 

 and upper surface is continued, as before stated, from the posterior ridge bound- 

 ing the temporal fossa : it is at first slightly convex, then slightly concave. The 

 upper surface of the zygoma is continued from the squamous plate of the tem- 

 poral, and extends three inches and a half anterior to the origin of the upper 

 angle of the zygoma, increasing in breadth as it advances, having a smooth and 

 concave surface, and terminating anteriorly by a rather sharp concave margin. 

 The under surface of the zygoma presents at its posterior part a broad and flat 

 articular surface for the lower jaw. From this surface the zygoma contracts to 

 its extremity, which is obliquely bevelled off from below upwards and forwards 

 to an obtuse termination above, which is wedged somewhat loosely into the upper 

 angular cleft of the large malar bone. 



