9 
groove. If a “supradentary” plate is present it has become so thoroughly 
coossified with the dentary that it can no longer be recognized as a separate 
element. 
At the upper posterior end of the left dentary (Figure 3 A) a short 
portion of the true border is preserved, which probably was in contact with 
the surangular. At first I was inclined to regard this border as a part 
of the dentary contribution to the boundary of a large mandibular foramen, 
but the high position in the ramus of such an opening seems to render such 
an hypothesis untenable. 
Measurements of Dentaries 
Mm. 
Greatest length of left dentary as preserved 193 
Complete length of dentary, estimated 230 
Depth of right dentary at 17th alveolus 19 
Depth of right dentary between 6th and 7 th alveoli 15 
Depth of left dentary between 4th and 5th alveoli 16-5 
Greatest width at anterior end of left dentary 8 
Greatest width at posterior end of left dentary 1 
Teeth. None of the fully functional teeth are preserved, although the 
basal portions of several are present in both dentaries. Fortunately the 
crowns of several germ teeth, not yet protrudent above the parapet of the 
jaws, and a single young tooth lacking the tip but which was about to 
come into use, are present. A study of these gives some clue to the character 
of the dentition and the method of tooth replacement. 
The teeth so far as they can be observed are compressed, subovate in 
cross-section, sharp pointed, recurved, serrate on posterior margins only. 
The method of tooth replacement is clearly shown in this specimen (Figure 
4). Several of the broken roots of functional teeth show the tips of the 
successional teeth protruding from their centres, and likewise smaller germ 
teeth are to be observed flattened against the inner anterior sides of the 
alveoli, ready to assume their proper positions when the roots of the preced- 
ing teeth have been sufficiently absorbed. 
c 6 a 
Figure 4. Diagrammatic view showing method of tooth replacement in Chirostenotea per- 
gracilis. No. 343, Geol. Surv., Can. a, functional tooth; b, successional tooth; c, germ tooth. 
Twice natural size. 
NOTES ON SOME UNIDENTIFIED VERTEBRAE 
In the palteontological collection of the Geological Survey, Canada, 
are a number of vertebral centra which possibly indicate the presence of 
an undescribed dinosaur in the Upper Cretaceous of western Canada. 
Reference is made to a dorsal and three caudal centra, No. 8504, probably 
of one individual, found by C. M. Sternberg in 1921, in the Lance formation 
on Rocky creek, southern Saskatchewan (sec. 7, tp. 1, range 4, W. 3rd 
mer.), and a single dorsal centrum, No. 8505, found by C. H. Sternberg in 
1913, in the Belly River formation, 3 miles below Steveville, Red Deer 
river, Alberta. 
