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other armoured dinosaur known to the writer and even when the dermal 
plate which covers it is included, it is very slender and weak. 
A large dermal plate covers the external surface of the mandibular 
ramus and extends below the level of the dentary, as well as covering it 
superiorly. This plate adds considerably to the breadth of the ramus 
where it is developed downward and outward just behind its midlength. 
Superiorly, this dermal scute develops into a broad, flat plate which covers 
that portion of the dentary normally occupied by teeth and forms a broad, 
flat, crushing or champing plate. This plate is broadest in its posterior 
half where it overhangs the internal border of the dentary. 
The dentary is edentulous, very slender, and, anteriorly, curves strongly 
inward to conform to the broadly rounded muzzle. The greatest height 
of the dentary, not including the dermal plate, is 27 mm. and its length is 
about 200 mm. Antero-internally, the dentary is subcircular in cross- 
section, cut off at right angles, and rugose. This would suggest that the 
predentary, which is not present with the specimen, did not separate the 
dentaries, but that they formed a strong union on the midline. About 
one-third of the superior border of the dentary is covered by the above- 
mentioned crushing plate. 
The splenial covers the internal face of the dentary and appears to 
extend almost or quite to the symphysis, though anteriorly the bones are 
so thoroughly fused that it is not possible to positively determine the 
extent of the splenial. 
Posteriorly, the mandible is very much depressed, the bones are 
thoroughly co-ossified, and there is no coronoid process. The mandibular 
cotylus is flat, oval in outline, and is located at the extreme posterior end 
of the ramus. Its greatest diameter, which is almost at right angles to 
the longer axis of the jaw, is 35 mm. 
Dimensions Of Skull And Mandible Of Type 
Mm. 
Greatest length of skull 372 
Breadth of superior surface just back of orbits 322 
Breadth of muzzle 212 
Height, lower border of mandible to above orbit 130 
Transverse diameter of external naris 75 
Greatest vertical diameter of external naris 20 
Greatest length of orbit. 67 
Greatest height of orbit 30 
From posterior edge of external naris to anterior border of orbit 140 
Length of mandibular ramus 245 
Greatest height of mandible, including scute. 40 
Distance between internal borders of distal ends of quadrates. 140 
Length of quadrate, about 115 
dermal armour (Plates XIX and XX) 
With the specimen are preserved about one hundred dermal scutes 
or plates, besides many small, shapeless ossicles. About a dozen of the 
scutes are of fair size and all are of the same general structure, though 
there is considerable variation in shape. Some are circular with a high 
central point (6), some ovate with a low keel, others long, narrow, high, 
thin-sided scutes, and still others are thin, flat plates. There is no sign 
of a ring of scutes as in Euoplocephalus and Ankylosaurus or of co-ossified 
nucal plates as in Panoplosaurus 1 and Edmontonia. 
1 Panoplosaurua mirus Lam be, Trans. Roy. Soc., Canada, sec. IV, PI. VI (1919). 
