PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 49 
The wall of the upper end of the first alveolus has been broken through on the right 
side. It lies on a level with the upper edge of the infraorbital foramen, and imme- 
diately behind the premaxillary suture. 
From what remains of the hinder alveoli and teeth, I suspect they become more and 
more nearly straight posteriorly. 
The external vertical contour of each tooth must be very similar to that of the max- 
illary surface between the upper end and the edge of the alveolus. 
The lateral faces of all the teeth are divided by two longitudinal grooves, placed 
opposite to one another on the two sides of each tooth, into three lobes. 
In the first tooth these grooves are very shallow, so that the thickness of the tooth, 
between the grooves, is far greater than the depth of a groove. In all the other teeth, 
the thickness of the teeth between the grooves, or of the isthmus by which the lobes 
of each tooth are connected, is much less than the depth of a groove. 
The view of the palate (Plate IV. fig. 3) shows that lines following the planes of the 
anterior surfaces of each of the four anterior teeth are directed inwards and forwards ; 
while in the sixth and seventh teeth, if not in all four posterior ones, such lines are directed 
inwards and backwards. The anterior surfaces of all the teeth, but the first, are concave, 
the posterior surfaces convex. The grinding-surfaces of all the teeth are directed a little 
outwards as well as downwards. Each surface is ridged in the middle and surrounded 
by a thin raised margin, and the general arrangement of the ridges is such that one is 
median, traversing the longitudinal axis of the grinding-surface, and three are disposed 
at right angles to these, in the longitudinal axes of the three lobes. The transverse 
ridges are continuous with the longitudinal, where they cut it (Plate V. figs. 3 & 4). 
Sometimes a transverse ridge may be bifurcated at its extremity, or accessory branch- 
lets may be given otf from the transverse, or from the longitudinal, ridges. 
A large pulp-cavity occupies the upper portion of each tooth ; but as its walls begin 
sensibly to thicken at about the junction of the upper and middle thirds of the tooth, 
the pulp-cavity diminishes in a corresponding ratio, and, rather below the middle of the 
tooth, it becomes obliterated. 
The Mandible * . — The lower jaw of Glyptodon is very remarkable, partly on account 
of the trough-like projection of the symphysis, but more especially by reason of its great 
height in relation to its length. The height, as measured from any horizontal surface on 
which the jaw is allowed to rest, to the summit of the articular condyle, is 9’25 inches; 
* Leaving aside for the present M. Nodot’s “ Schistopleuron,” the only fragment of the lower jaw of Glyp- 
todon clavipes yet described is that mentioned in the Catalogue of the Royal College of Surgeons under 
“ No. 517. A fragment of the anterior part of the left ramus of the lower jaw, including portions of the 
sockets of the anterior teeth. The first is small and simple, and is situated close to the anterior termination of 
the dental canal ; the second socket shows, by the two prominent vertical ridges on its anterior and posterior walls, 
that the tooth which it contained had the fluted form characteristic of the genus ; the third socket, which is the 
most complete, differs from the preceding in a slight increase of size, and it shows that the tooth was implanted 
by an undivided base of considerable length, and of the same size and form as the exposed part or crown.” 
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