328 PROF. T. W. BRIDGE ON THE MORPHOLOGY OF THE SKULL 



portion of the skull which lies posterior to the nasal capsules, varying, however, in 

 their relations to the cranial cavity and to the chondrocranium in different regions. 

 Thus, in the anterior part of their extent (figs. 1, 4, and 15), the lateral portions of 

 the bone, after forming the roof of the cranial cavity, curve sharply downward to the 

 inner side of the trabecular cartilage, and by it are separated from the palato-pterygoid 

 bone (fig. 15), eventually terminating on each side in an obliquely-fissured and some- 

 what irregular inferior margin (fig. 4), without, however, quite meeting the cartila- 

 ginous plate which, in front of the parasphenoid, forms the cranial floor. More 

 posteriorly the fronto-parietal, as it descends from the roof into the side-walls of the 

 cranial cavity, meets on each side the upturned lateral margin of the parasphenoid 

 (figs. 4, 16, and 17) in a broadly V-shapecl suture, which is best seen in a vertical 

 longitudinal section of the skull (fig. 4), but is hidden externally by the trabecular 

 cartilage (fig. 1, tr.c). More posteriorly still (figs. 17 and 18) each lateral portion of 

 the bone is continued outward from the cranial roof, externally to the cartilaginous 

 auditory capsule, and thence is prolonged downward and outward in close relation 

 with the outer surface of the suspensorial cartilage, extending almost as far as the 

 articular surface for the mandible ; eventually the bone tapers to a contracted apex, 

 which is wedged in between the hinder part of the palato-pterygoid bone and the 

 squamosal, articulating with the superior margin of the former and the anterior borde 

 of the latter (fig. 1). Behind the auditory capsule (figs. 1 and 19) the fronto-parietal 

 overlies the cartilage of the supraoccipital region, and its lateral margins, converging 

 from below upward and backward, project beyond the chondrocranium, and, after 

 overlapping the two exoccipital bones and the first neural arch, terminate dorsally in a 

 backwardly-projecting conical process (figs. 1 and 2). The converging lateral margins 

 of the bone simulate the appearance of the characteristic "lambdoid" crest of the 

 carnivorous Mammalia (fig. 2, Icl.c), and serve for the insertion of a portion of the 

 lateral musculature of the trunk. From what has been stated as to the extent and 

 relations of the fronto-parietal bone, it is obvious that it forms not merely the roof 

 but also the lateral walls of all that section of the cranial cavity which lies between 

 the mesethmoid region anteriorly and the auditory capsule posteriorly, and further, 

 that in addition to strengthening the cranial roof in the auditory and post-auditory 

 regions of the skull, it also contributes to the rigidity of the articular condyle for the 

 lower jaw by investing the outer surface of the suspensorial cartilage. 



Anteriorly to the fronto-parietal, and resting on the cartilaginous internasal septum, 

 and also extending laterally so as to partially invest the fenestrated dorsal walls of the 

 olfactory capsules, is a relatively thick and somewhat triangular bone (PI. XXVilL 

 figs. 1, 2, and 4 ; PI. XXIX. figs. 11 and 12, (I.e.). The broad hinder margin of the 

 bone is connected by a tough fibrous tissue, and not by suture, with the anterior edge 

 of the fronto-parietal (fig. 4), and from this point the bone gradually contracts to a 

 blunt apex which terminates a little posterior to the laterally-diverging cornua 



