146 The Ottawa Naturalist. [Feb. 



separated from the jugal by a small quadrato-jugal. Mandible 

 robust. Predentary expanded laterally and deflected in its 

 hinder half, and posteriorly bifurcated below at the midline. 

 Neural spines of the anterior dorsal vertebrae long. Ischia 

 not expanded distally. Body covered with small, polygonal, 

 non-imbricating, tuberculate scales of rather uniform size. 



In no other member of the Trachodontidae is the skull so 

 deep anteriorly as in Gryposaurus notabilis. The nasals rise to an 

 extraordinary height a short distance in advance of the orbits. 

 The top of the curve of the nasals is as high as the highest point 

 of the back of the skull, viz., the summit of the squamosal 

 behind the supratemporal fossa. The depth of the head at the 

 apex of the nasal bones is equal to about half the maximum 

 length of the skull. 



For the present, the characters of the species will be taken 

 for the most part from the skull. 



Vii :'rom the side, the superior outline of the head is 



most depressed above the front border of the orbit, rising 

 abruptly forward by a short ascent to the summit of the nasals, 

 w T hence it descends rapidly to the anterior end of the premaxilla 

 in a long curve whose general convexity is broken by a slight 

 dip at midlength. From above the orbit the outline slopes 

 gradually upward to attain the highest posterior point of the 

 dorsal surface of the head a little in advance of the upper end of 

 the quadrate. 



Seen from above, the broadest part of the head is along the 



"ace of the jugal beneath the lateral temporal fossa, whence 



it contracts upward to the dorsal surface and forward to a point 



oath the hinder end of the nasal opening, to expand again 



to a moderate extent in the lower premaxillary border. 



In the dorsal surface of the skull there is a slight diminution 



in breadth from behind the orbits backward, a somewhat equal 



contraction forward above the orbits, continued in a much 



greater degree, in the front half of the skull, by the narrow 



dian elevation of the nasals and premaxillse. 



The sutures in this skull are so distinct that the position, 

 shape and connections of the various elements composing it can 

 be readilv understood by reference to its photographic re- 

 -entation in lateral aspect in plate XVIII. 



The narial opening is extremely long and narrow. It is 

 enclosed behind and mostly above by the nasal, and in front, 

 and for the greater part below, by the premaxilla. 



The orbital opening is higher than wide, somewhat quad- 

 rangular in outline, and narrower below than above. The upper 

 rim is formed equally by the prefrontal and postfrontal, and has 

 a rugose surface. In the rim between these bones is wdiat appears 



