1917] The Ottaava Naturalist. 71 



Vomer. This element appears to have been slender throughout 

 and devoid of any considerable expansion. It is known in Edmonto- 

 saurus only from a small portion preserved in the type skull, plate II; 

 the piece is over 125 mm. long and lies in the midline of the skull 

 under the posterior half-length of the narial opening. It apparently 

 connected in front with the maxillaries on the inner side of their 

 anterior processes, and behind with the pterygoids on the interno- 

 superior surface on the height of their anterior wings. It appears to 

 have been narrow between the maxillary processes and to hav r e had a 

 slender termination in advance of them. Whether the vomer bifurcated 

 behind and reached the pterygoid on either side in this manner, or 

 united with the pair by a horizontal expansion has not been ascer- 

 tained. It is estimated to haA T e had a length in the figured skull of 

 over 400 mm. 



Angular. Is long, narrow, and thin, and is in sutural contact 

 with the splenial, surangular, and dentary, running forward from a 

 short distance in advance of the hinder end of the surangular, on the 

 inner side of that bone, to a point on the dentary about in line with 

 the midlength of the dental magazine. In lateral aspect it inclines 

 slightly upward in one-third of its length posteriorly. Viewed from 

 above it has a flattened sigmoid curve, suiting itself to the inner con- 

 vexity of the surangular and the concavity of the lowermost part of 

 the dentary. Superiorly, for its posterior half-length, it meets the 

 loAver border of the splenial. 



Splenial. A moderately thin bone, shorter than the angular, 

 applied anteriorly to the inner face of the dentary, and posteriorly to 

 the inner face of the articular. Its lower border is in contact with the 

 angular. It is deepest near the front where its superior border curves 

 outwardly over the supero-internal termination of the dentary behind 

 the dental magazine; farther forward it narrows rapidly to a point in 

 contact with the dentary below the hindermost dental foramina. In 

 the posterior two-thirds of its length it lessens but slightly in depth 

 backward, and apparently terminated with a rounded lateral outline. 

 It reaches farther back than the angular and is in contact with it for 

 nearly the whole of the latter's half-length. Its inner face is moder- 

 ately concave in a longitudinal direction. 



Surangular. Is large and robust in comparison with the angular, 

 splenial and articular, in conjunction with which it adds considerably 

 to the length of the mandibular ramus, as the lowermost element of 

 the mandible behind the dentary. It is through this bone, with a slight 

 assistance from the articular, that the attachment of the mandible to 

 the quadrate is effected. It articulates in front with the dentary, 

 postero-superiorly with the articular, and laterally on the inner side 

 with the angular. It consists of an oblong main portion, longer than 

 broad, from which is given off antero-exteriorly a thin, ascending 



