57 
emarginated at the base into which the next succeeding tooth closely 
fits. There is a slight elevation of the margins, but most of the larger 
dentary teeth appear to be devoid of papillations in No. 8501, though they 
are more evident in the dentary of No. 8500. The smaller anterior teeth 
in dentary No. 8500 are more strongly papillate than those situated more 
posteriorly. There could hardly have been more than three complete 
teeth in any one vertical series. The number of teeth in wear at one tim e 
in the cutting edge cannot be determined from these specimens. 
Figure 16. Teeth from dentary illustrating the type of dentition in the central part of the 
series. No. 8501, Geol. Surv., Can. Natural size. 
Although the evidence accumulated is scarcely extensive enough to 
base conclusions upon, it indicates that with the shortening of the skull, 
as in the sub-family Lambeosaurinse, there has been a considerable reduction 
in the number of tooth rows and a relative narrowing and lengthening 
of the individual teeth. In both these respects the teeth of Cheneosaurus 
show the most extreme specialization. From a compiled table, based on 
all available sources of information, it has been determined that none of 
the members of the Lambeosaurinse exceed 41 vertical rows of teeth in the 
dentary, and all but one genus has less than that number. 
All other members of the Hadrosauridse in which the dentary series 
has been determined show a greater number, with the possible exception 
of Parasaurolophus, and the skull structure indicates that its affinities 
are within the sub-family Lambeosaurinse rather than the Saurolophinse, 
its present assignment by Parks 1 . Accumulating evidence, slight as it 
may be at the present time, all points to the probability that in the near 
future the differences to be observed in the dentition of these animals will 
furnish important characters to assist in the proper and more exact classi- 
fication of the Hadrosauridse. 
1 University of Toronto Studies, No. 13, 1922, p. 5. 
