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and hence, because of the bend in the bone at this place, mor- 

 phologically lateral to, the most lateral tooth of the bone. On 

 the dorsal surface of this part of the bone there is no apparent in- 

 dication of the fusion of the two independently formed components 

 of the bone, the one related to and enclosing the lateral canal, and 

 the other related to and bearing the teeth. Viewed from behind, on 

 the contrary, the canal bearing part of the bone looks decidedly like 

 a separate cylindrical bone fused with the dorsal surface of the under- 

 lying plate-like palatine process, which process seems to arise entirely 

 from the tooth-bearing part of the bone. 



Posterior to this anterior, tooth-bearing portion of the bone, the 

 premaxillary may be said to consist of two portions, the one lying 

 between tubes 4 and 5 infraorbital, and the other lying dorso-posterior 

 to tube 5. The part that lies between tubes 4 and 5 is a short 

 cylindrical piece of bone that lies immediately ventro-lateral to, and 

 forms part of the boundary of, the external opening of the nasal 

 chamber. Both anteriorly and posteriorly this piece of bone presents 

 strongly the appearance of overlapping externally, and being fused 

 with, the other two portions of the bone, this appearance being especi- 

 ally marked where it joins the posterior portion, the hind of the canal 

 component here standing out so as to form a projecting corner in the 

 bone. This part of the bone thus forms a relatively narrow bridge con- 

 necting the larger, anterior and posterior, portions. Its ventral sur- 

 face is rounded and smooth, and fits into a slightly hollowed, longi- 

 tudinal facet on the dorsal edge of the anterior end of the so-called 

 maxillary bone. The two bones are here strongly bound together by 

 connective tissues but some slight movement is possible between them, 

 the maxillary swinging, latero-mesially, upon the under surface of 

 premaxillary. 



The posterior portion of the premaxillary is a plate of dermal 

 bone that lies against and almost completely covers the lateral sur- 

 face of the antorbital process of the skull. Its dorsal edge is thickened, 

 and rests against the ventral surface of the lateral edges of the ad- 

 joining nasal and frontal bones. The anterior end of this dorsal edge 

 of the premaxillary projects slightly forward, as a small sharp process, 

 while its hind end is prolonged as a long sharp process. The anterior 

 edge of this posterior portion of the premaxillary is thus concave, 

 and bounds a posterior portion of the opening of the nasal chamber. 

 The hind edge of the bone rests upon, and is firmly attached to, the 

 roughened lateral edge of the prefrontal of Traquair's descriptions. 



