162 



for their lower half. A line drawn touching the most posterior 

 parts of both condyles lies almost exactly in the occipital plane. 

 No indication of a separate interparietal exists, nor can the out- 

 line between the occipital and parietal bones be distinguished ; 

 but at the juncture of the occipital plane with the vertex, and 

 defining the limits of the former area, a well-marked almost 

 semicircular occipital ridge occurs, which disappears at the 

 level of the posterior (or upper) margin of the occipital condyles. 

 Prom the occipital tubercle a slight vertical ridge runs down- 

 wards almost meeting the occipital foramen. On the vertex of 

 the skull, a ridge for muscular attachment runs forwards and out- 

 wards, and then downwards from the occipital tubercle, till it 

 iDecomes continuous with the upper edge of the zygoma. Close 

 behind, and parallel to this ridge, are two smaller ridges which 

 become merged into that just described at a point before it 

 reaches the zygoma. (PL VI. and VII., fig. 1.) As between the 

 •occipital and parietal bones, no delimitation between the parietals 

 and squamosals, or between the parietals and frontal, can be 

 •distinguislied. 



In front of the skull, the sutures can be distinguished, and 

 the shape and extent of the nasals, superior maxilla?, premaxillai 

 and part of the lachrymals are as shown in fig. 1, PI. VI. and 

 VII. In the position of the opening of the lachrymal canal is a 

 well marked circular depression, due to thinning of the bone ; 

 but I am unable to detect any patent orifice. The infraorbital 

 foramen is large and transmits a very large nerve. The malar 

 cannot be made out as a separate bone, but, springing from the 

 malar region, opposite the penultimate molar tooth, proceeds a 

 well marked zygomatic arch, so much compressed laterally through- 

 out that it forms a thin vertical lamina, very narrow in front, but 

 gradually widening as it jjroceeds backwards, until, in its posterior 

 half, it becomes relatively very wide ; a portion of its hinder 

 end enters into the formation of the articular surface for the 

 lower jaw, and forms a marked preglenoid prominence. The 

 junction of the arch with the squamosal is close to the cranial 

 part of the latter, so that very little of the arch itself is formed 

 by the latter bone. The length of the arch is to that of the 

 whole skull almost exactly as 1 to 3. 



Behind, the glenoid surface is formed chiefly by the squamosal, 

 wdiich projects externally in the form of a reversely placed C-shaped 

 ridge, the lower limb of the ridge running forwards and down- 

 wards and bounding the upper and front part of the auditory 

 meatus, then, losing itself in the tympanic part of the auditory 

 bulla, which latter projects forward under the glenoid cavity. 



The auditory bulla (PI. VI., fig. 1 ; and PI. VII., fig. 2) is large 

 :a,nd conspicuous, but has throughout exceedingly thin and fragile 



