13 
assignment to the different genus. Members of this genus seem to have 
been more primitive than other described hooded hadrosaurs from the Pale 
Beds. In many respects Tetragonosaurus resembles Cheneosaurus of the 
Edmonton formation (8), but the open narial slit, less advanced nasal, 
.steeper facial slope, and differently shaped jugal, as well as the great differ- 
ence in geological age, seem sufficient grounds for their separation. 
Tetragonosaurus cranihrevis sp. nov. 
Plate IV, figure 1 
Type. No. 8633, Geol. Surv., Canada, consists of complete skull and 
jaws except predentary, left lachrymal, jugal, quadrate, quadrato jugal, and 
the small bones of the left ramus. Collected by the writer, 1928. 
Horizon. Pale Beds, Belly River series, Upper Cretaceous. 
Locality. 2£ miles south of mouth of Berry creek, 140 feet above Red 
Deer river, Alberta. 
Generic Characters. Skull short, high, and blocky; brain-case not 
strongly deflected; hood low in advance of orbit, not overhanging cranium; 
lower limb of premaxillae extending backward, not separating upper limb 
and nasal; upper limb of premaxilla overlapping nasal posteriorly; nasal 
narrow and extending far forward; open slit above narial passage; narial 
passage enters upper limb of premaxilla through S-shaped tube; frontal 
long; lachrymal well developed; teeth more numerous in maxilla than 
dentary; jugal long and slender. 
Specific Characters. Skull relatively large; cranium short; hood rela- 
tively high; facial slope gentle anteriorly, then sharply up-turned above 
maxilla; lower edge of premaxilla folded to cover narial passage except 
for narrow slit; posterior extremity of lower limb of premaxilla above 
centre of orbit, superior edge uniting with upper limb just in advance of 
tip of nasal; frontal and prefontal up-turned to unite with nasal; anterior 
prolongation of nasal flanking but not overlapping upper limb of pre- 
maxilla; dentary heavy and strongly decurved anteriorly; 40 teeth in 
maxilla and 33 in dentary; dental magazine in dentary deep, usually 4 
teeth in vertical series. 
The skull is larger and that portion behind the hood is relatively much 
shorter than in the types and only known representatives of the two species, 
described as Tetragonosaurus praeceps and T. erectofrons by Prof. Parks. 
The dome or hood is in a much more advanced stage of development, yet 
the open sutures suggest that it represents a less mature individual than 
either of the other specimens. Parks shows the narial passage as being 
open superiorly to above the orbits. In the present species this region is 
very similar to that seen in C. excavatus above described. Parks states 
(15) that “the exterior nares are of extraordinary length”. It is hardly 
conceivable that the external nares occurred as long, narrow slits. It is 
the opinion of the writer that the external nares were located near the front 
of the premaxilla in all of the hooded hadrosaurs and probably in the other 
forms as well. When viewed from the side the skull resembles that of 
T. praeceps , but the hood is higher and longer. It has not, however, reached 
3312—2 
