67 



The parietal element Irom Red Deer river is symmetrical, T-shaped, wth a sub- 

 cyliudrical shaft expanding rapidly both in front and behind. Anteriorly the expansion 

 is concave below, strengthened above by a median, rounded ridge in continuation of the 

 central shaft, and thinning out laterally. Posteriorly the shaft divides, nearly at right 

 angles to itself, to either side, so as to form a strong transverse bar slightly concave at 

 mid-length above and convex below, thin at its front edge and thickest behind. The 

 posterior border is angularly rounded. 



The space on either side of the shaft represents the inner halves of the supra- 

 temporal fontanelles. The bone missing from the specimen would complete the outer 

 border of the fontanelles and effect a union with the inner margins of the squamosals- 

 The lower face of the anterior expansion, on either side of the median line, is striated by 

 distinct furrows that follow down the lower lateral sides of the shaft, as deep grooves, 

 and curve outward on to the transverse bar. The anterior upper surface also exhibits 

 similar grooves that do not, however, pass beyond the mid-length of the shaft. 



The parietal, imperfect at its anterior end, is about one-third the size of that of T. 

 gladius and would probably represent a proportionately smaller animal, an earlier and 

 more generalized form of the genus with larger fontanelles than its later Laramie 

 successors. 



Measurements of parietal bone, 



M. 



Extreme length of specimen (imperfect anteriorly) along median line 584 



Breadth of front expansion from median line to left edge of specimen 'ITS 



Breadth of posterior border from median line to left edge of specimen , -305 



Circumference of shaft at mid-length • 180 



Breadth of same at mid-length • 065 



Thickness of same at mid-length ■ 063 



Thickness of anterior expansion at centre on median line -041 



Thickness at anterior end of specimen on median line ... -018 



Thickness on median line midway between posterior border and narrowest part 



of shaft - 035 



Antero-posterior diameter of fontanelles • 416 



Belly Eiver series, Red Deer river, 1898. 



This species is dedicated to Dr. Robert Bell, the administrative head of the Geologi- 

 cal Survey. 



Amer. .Jour. Sci. and Arts. 1S91, vol. xlii., p. '266. Ibid, 1S92, vol. .\Iiii., p. SI, plate ii. 



