184 KANSAS UNIVERSITY QUARTERLY. 
a long slender pit just back of it on the internal side. It is more 
elliptical than the corresponding } it in Saurocephalus. The lower 
border of the bone is sharp. 
In a paper recently published by Prof. Hay *U. S. N. M. the 
author corrects some errors in the former descriptions of the jaws 
of X7phactinus. 1 have for sometime been of the opinion that the 
bones of this region had not been correctly interpreted, and as the 
arrangement of the articular portion of this genus, seems to agree 
with the figure and description of this part of Xzphactinus as given 
by the author, I think it well to adopt his nomenclature. , 
The dermarticular supports only a small portion of the cotylus, 
in the lower portion of the cavity. It sends a long sword-shaped 
process forward internally, but does not encroach much upon the 
dentary externally. Posteriorly, it sends a lamina of bone back- 
ward, which I think would be well named the cotyloid process as 
in most of the genera of this family; it is the only portion of this 
bone which articulates directly with the quadrate. Just beneath 
the cotyloid process, there is a prominent angle. 
The autarticular is a small element not extending forward beyond 
the sixth posterior tooth, and is fitted into a groove in the dermar- 
ticular. It supports nearly the whole of the cotylus, which is some- 
what elliptical and concave from above downward. The preden- 
tary is not so elongated but is slightly deeper than in the species 
described above. 
MEASUREMENTS OF MANDIBLE. 
mm 
Mandible; lengthvotalveolan border: 2s een aca. anette a yee ia ee 149 
& length -tromucotyloidicavityare’ sa acca ah ie ee. ieee ete 174 
depth atisymphysisy ee wi ies Jeni askn become toe Ca eee By 
depth’ at: GOrOMOIG.,. (8.5 lee ela nde eaten ely alee PaO aa eee 46 
ninmber Oh teethomn Sr. AG am Lees ee, Cotes, ans epee eee 3 
Predentary. wleme thy :.2. cinta rena sy che tote tens caehas ASTER Wy SRT TOME ee Sa ce 55 
lengthiot.symphysealssuinbaCeiamy.. -csn\ tien aerate) eee OA 
The quadrate is a broad fan-shaped expansion. The condyle is 
elliptical in outline and convex. Extending upward from the 
condyle on the external side there is a ridge which ends above in 
a deep notch which accommodates a portionof the sympletic. This 
groove continues downward on the internal side for more than 
one-half the depth of the bone. The posterior border has a very 
slight groove and extends upward the whole extent of the sym- 
pletic. The superior border probably articulates with the ptery- 
goid and metapterygoid as in X7zphactinus. The anterior border is 
sharp. Both the external and internal surfaces are covered with 
*Zoological Bull., vol. ii, No. 1, pp. 36-38. 
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