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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



strong bracing is concentrated into a short rounded transverse column at the end of the 

 junction of the parietal and pterotic. This must resist lateral compression occasioned by 

 the thrusts of the suspensorium of the upper jaw, and it must strengthen the attachment 

 of the high crest on the parietal that divides the trunk muscles into one lower and two upper 

 strands. 



The greatest massing of trabeculae and dense bone occurs, however, near the junction 

 of the occiput with the vertebral column. Whereas strengthening in this region was effected 

 by the incorporation of the centrum of the first vertebra into the occiput, in Luciolates per- 

 haps a still better arrangement is hit upon by having the occipital condyle tripartite, with 

 three inclined condylar articular surfaces, furnished respectively by the basi- and ex-occipi- 

 tals. Thus dorso-ventral dislocation, with resulting strangulation of the spinal cord, is 



Fig. 118. Lates niloticus. Top view. 



prevented by the overhang of the exoccipital upon the basioccipital segments, while lateral 

 dislocation is prevented by the lateral obliquity of the exoccipital facets. Here then is an 

 interesting parallel to the tripartite occipito-atlanteal facets of certain extinct reptiles and 

 stegocephalians. 



