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of the supraoccipital. The thin plate tliat forms this part of the bone projects posteriorly beyond 

 the flange that forms the posterior surface of the bone, the two plates forming part of the roof and 

 part of the bottom (antero-lateral corner) of a large fossa on the posterior surface of the skulL The 

 postero-kteral end of the flange that forms the posterior surface of the bone, and adjoining portions 

 of the lateral edge of the bone, suturate respectively with the pedicle and body of the suprascapular. 



The SUPRAOCCIPITAL, the interparietal of Cuvier and Valenciennes' descriptions, has 

 the usual dorsal and ventral limbs, and a large spina occipitalis. The dorsal limb of the bone, with 

 the exception of two small lateral processes on either side, comes everywhere to the outer level of 

 the dorsal surface of the skull, and has surface markings exactly similar to those on the adjoining 

 dermal bones; and this apparently dermal portion of this limb of the bone extends posteriorly 

 slightly beyond the line of origin of the ventral limb, onto the dorsal surface of a dorsal plate-like 

 portion of the spina occipitalis. This limb of the bone suturates anteriorly with the frontals, laterally 

 with the parietals, and posteriorly with the mesial extrascapulars; its anterior edge resting, on 

 either side, upon the hind end of the expanded dorsal surface of the brace-Hke ridge on the internal 

 surface of the alisphenoid. On the ventral surface of the dorsal limb, beginning immediately anterior 

 to the line of origin of the ventral limb, there is, on either side, a small ridge which, extending antero- 

 laterally is continuous with that tall ridge on the internal surface of the proötic that forms the anterior 

 wall of the labyrinth recess. The antero-lateral end of this ridge on the supraoccipital forms one of 

 the two lateral processes on either side of the dorsal limb of the bone, the other process lying 

 immediately posterior and parallel to it, giving support on its dorsal surface to the parietal, and being 

 in synchondrosis, by its postero-lateral edge, with the antero-mesial edge of the epiotic. 



The ventral limb of the supraoccipital is irregulär, as shown in the figures, and has on either 

 side a strongly concave dorsal and convex ventral surface. Along the median line of the limb a thin 

 median vertical plate of bone arises supported on either side by a similar but slightly inclined plate, 

 these three plates forming the vertical portion of the spina occipitahs. This vertical portion of the 

 spina Supports, on its dorsal edge, a flat broad thin plate which forms a direct posterior extension 

 of the dorsal limb of the bone, and gives support, on either side of its dorsal surface, to the corres- 

 ponding mesial extrascapular. The lateral edge of the anterior end of this flat portion of the spina, 

 on either side, rests upon and is coalesced with the dorsal edge of the lateral portion of the ventral 

 limb of the bone, a deep pocket thus being formed on either side of the posterior surface of the bone, 

 this pocket forming the dorso-mesial corner of a large fossa on either side of the hind end of the skull. 

 The posterior half of the ventral surface of the ventral limb of the bone rests, on either side, on the 

 dorsal edge of the medullary plate of the corresponding exoccipital, either suturating or being in 

 synchondrosis with that bone. Lateral to the exoccipital, the ventral limb of the supraoccipital 

 is in similar contact with the mesial edge of the epiotic. 



There is no separate OPISTHOTIC bone, nor is there any indication of the fusion of this bone 

 with any of the other bones. 



The primary bones, and their relations to the dorsal surface of the primary skull, now having 

 been described, the dermal bones that overlie them and form the casque-Hke dorsal surface of the 

 skull can be described. 



The two .NASALS have fused in the median line to form a single median bone, and have 

 already been described. 



