CHIONIS MINOR. 99 



properly speaking, incomplete only as regards the irregular foramen 

 above mentioned. It is marked anteriorly by prominent stout bridges 

 of bone, disposed so as to form the letter Y, which are continuous 

 apparently with the notable exostosis marking the anterior portion of 

 the frontal bone. 



Parietal and temporal bones are not distinctly limited, owing to the 

 complete ossification of the brain-case. The external auditory meatus 

 is large, and so well protected by its surrounding periotic processes as 

 to seem to be almost a tubular prolongation of the skull. 



Os quadratum is in shape somewhat like a molar tooth, its crown be- 

 iug directed downward, and one fang {i. e. orbital process) projecting 

 upward, forward, and inward nearly to the body of the basisphenoid. 

 It presents five articulating facets ; one inferior, broad, triangular, and 

 marked by three marginal mammillse, for the mandible; one external to 

 and a little above this, for the zygoma ; two, on its upper surface, for 

 articulation with the temporal ; and one, internal to these, for the 

 pterygoid. 



Pterygoids are relatively slender, 0.32 inch long, flattened from side 

 to side, and slightly twisted ui)on themselves. They diverge from the 

 palato-pterygoid articulation at an unusually wide angle, rather more 

 than 90O. 



Vomer is long, slender, bifid posteriorly, apparently extending from 

 pterygo-palatine articulation to beyond the anterior extremity of the 

 maxillo-palatines. Its complete anchylosis with the palatines, however, 

 renders it impossible to determine exactly its posterior limit. Its su- 

 perior surface is deeply channeled for its whole length. Beneath the 

 vomer are to be found the maxillo-palatines and palatines^ the latter 

 soldered together on each side, but quite separated in the middle line. 



Palatines are thih laminae, irregularly concavo-convex. They present 

 two prominent laminae, external and internal. The external, which con- 

 stitutes most of the bone, flares widely outward and downward, ending 

 behind transversely, yet with a gontly-rounded angle. From its under 

 surface descends obliquely inward the much smaller internal lamina, 

 like a keel. 



Maxillo-'pala tines. — These bones are ratlier stout, squarish, tumid bod- 

 ies, anteriorly joining the palatines at a point, but in all the rest of their 

 extent entirely separated therefrom, as they also are from the vomer 

 and from each other. The "body" is a very thin osseous wall, inclosing 

 a hollow cavity. Anteriorly the palatines are produced as maxillary 



