ART. 16 FOSSIL KEPTILES PROM MONTAE"A GILMOEE 5 



its perfection. Unfortunately most of the sutures are obliterated, 

 making it quite impossible to determine the extent of many of the 

 elements. Except for differences in proportion, the palate structures 

 seems to be identical with Edmontonia longiceps as described by 

 Sternberg.*^ 



The outstanding peculiarities of structure observed in the palate 

 of this specimen are the ladle-shaped form of the premaxillary re- 

 gion; the division of the mouth longitudinally by a vertical plate 

 of bone that extends backward from the median junction of the 

 premaxillaries ; the great shortening of the pterygoids, the inward 

 curvature of the tooth rows, and the wide overhanging buccal area 

 along the outer sides of the maxillary bones. 



The edentulous premaxillary bones form the greater part of the 

 large rectangular muzzle. As mentioned above, their combined 

 inner surfaces are hollowed out, in form suggesting a ladle. The 

 outer anterior borders curve strongly downward, forming a sharp 

 cutting edge that in life was doubtless covered by a chitinous sheath. 

 On either side external to this sharp ridge of bone the premaxillaries 

 are widened by dermal bones that are firmly coossified to it. A low, 

 subacute median ridge rising on the anterior third extends backward 

 to the junction with the prevomers. On either side of the midline 

 the premaxillaries are pierced by small rounded foramina that lead 

 upward and forward through the floor of the anterior nares. The 

 sutures between premaxillaries, maxillaries, and prevomers are clearly 

 determinable as shown in Figure 2. On the right side the border of 

 the premaxillary shows deformation in the form of a notch, evidently 

 due to an injury received in life, since the edges of the bone had 

 healed as indicated by their rounded borders. 



The maxillae have the greater portion of their outer surfaces 

 hidden by the covering of dermal bone. Anteriorly they meet the 

 premaxillae, internally the prevomers, and toward the posterior end 

 the ectopterygoids. The striking characteristic of these bones is the 

 curved nature of the dentigerous border. The teeth are borne on 

 a downwardly descending plate that gradually recedes in height 

 toward the front. The tooth rows are wide apart posteriorly (144 

 mm.), but curve in rapidly to a point forward of their mid-length 

 where they become parallel. In front the teeth of opposite sides are 

 only 77 mm. apart, exactly half the space of the posterior ones. 

 There are sixteen alveoli in each maxillary bone, and these occupy 

 a space of 120 mm. measured in a straight line. Judging from the 

 relative sizes of the alveoli, the teeth decrease in size from back 

 to front. 



« Trans. Roy. Soc. Canada, vol. 22, 1928, pp. 98-100, pi. 2. 



