48 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 
fig. 1), so as to be convex in front and concave behind. Its inner edge is thick and 
rounded, except towards its termination, where it presents some slight irregularities or 
cligitations. The outer edge is comparatively thin and rugose ; it is bevelled off inte- 
riorly, and more obliquely on the right side than on the left. The inner part of the 
front face of the process looks almost directly forwards, and is very smooth ; but the 
outer part of that face looks outwards more than forwards, and is rugose (Plate YI. 
fig. 1). The hinder, concave face of the process (Plate VI. fig. 2) is divided by an 
oblique ridge (b), which passes from its superior and external to its inferior and internal 
angle into two areee — an inner, smooth, and an outer, rough and tuberculated. The 
superior and external part of the process, where it was doubtless continued into the 
zygoma, is evidently fractured. The root of the zygoma is perforated near its origin by 
a large, oval, infraorbital canal, the lower edge of which is rather more than an inch 
distant from the lower margin of the root of the zygoma. The canal is short, and is 
directed forwards and outwards. 
The lachrymal foramen is a round aperture, placed upon the anterior edge of the orbit, 
T6 inch above the infraorbital canal (Plate V. fig. 1, b). 
The internal walls of eight alveoli, on each side, are preserved. The external walls 
<of the anterior four upon the left side, and of the anterior three upon the right side, 
•are almost entire ; but, posteriorly, the external walls of all the other alveoli, upon each 
side, are broken away (Plate V. fig. 1). 
Measured in a straight line, the eight alveoli occupy a space of 8 inches, and each 
alveolus is, on an average, 0*9 inch long. The teeth which occupy the alveoli are sen- 
sibly equal in long diameter ; but the anterior tooth is much narrower than the others, 
measuring only 0‘35 inch in this direction, while the other teeth have a transverse 
diameter of 06 inch, or nearly double that of the first. 
None of the teeth are entire upon the right side. Of the left series, the crowns of 
the first, third, fourth, and sixth are in very good condition, while the second is much 
damaged ; of the fifth, only the middle lobe exists, and of the seventh only the two ante- 
rior lobes (Plate IV. fig. 3). 
The alveoli are exceedingly long, and the outer walls of the third and fourth, on each 
side, are so much broken away, that the whole length of their alveoli can be observed 
and measured. The fourth is 4*5 inches long, and bends outwards and forwards as it 
passes upwards, to terminate nearly on a level with the lachrymal foramen. The tooth 
which filled the alveolus must have had a corresponding length and curvature ; for the 
two longitudinal ridges of bone, which partially subdivide the alveolus into three 
chambers near its free end, are continued quite up to its closed extremity, and are 
lined by a shell of dental substance, which gradually thickens below and becomes 
continuous with the body of the tooth (Plate Y. fig. 1. 4, 4'). 
The third alveolus presents the same general curvatures as the fourth, but is inclined 
somewhat further outwards at its upper end, which lies close to, and about an inch above, 
the hinder end of the infraorbital foramen. 
