44 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 
is very imperfect — the entire roof and sides, and the greater part of the base of the 
skull being absent, while a small portion only of the sphenoidal region is preserved. 
Of the facial bones, those entering into the palate are preserved almost in their 
entirety, and one ramns of the lower jaw is nearly complete. This skull therefore 
supplies almost all those parts which were wanting in the cranium of the type speci- 
men, in which the whole of the roof of the skull, from the nasal bones to the supra- 
occipital inclusive, most of the exoccipital, alisphenoidal, and orbitosphenoidal regions 
of the lateral walls, and of the basioccipital, basisphenoidal, and presphenoidal parts 
of the base, together with the temporal bones, are in good condition, while the premax- 
illary, maxillary, and palatine bones, with the mandible, are absent. 
In order to give a tolerably complete view of the structure of the skull, I shall, in the 
first place, describe that of the new specimen ; I shall next proceed to a comparison 
of the parts common to this fossil and the skull of the type specimen, in order to 
demonstrate the specific identity of the two ; and then I shall endeavour to supply what 
is wanting in the new specimen by information derived from the study of the type. 
The skull of the new specimen of Glyptodon clavipes. — The anterior nares have a 
trapezoidal form, the upper of the two parallel sides of the trapezoid being nearly three 
times as long as the lower, so that the two lateral boundaries converge from the roof 
towards the base of the nares (Plate VI. fig. 1). 
The upper boundary of the anterior nares is formed by the anterior edges of the thick 
nasal bones, which are bevelled obliquely from below upwards, and so rounded off late- 
rally that the contour of the two forms a large arc of a circle, the chord of which 
measures 3-4 inches (Plate IV. fig. 1). The upper surface of each nasal bone is rough 
and perforated by many vascular foramina, which open forward ; and the two nasal bones 
are separated by a suture, which can be traced backwards in the middle line for 2'2 inches, 
and then comes to an abrupt termination. I presume that the extent of this suture 
indicates the distance to which the nasal bones reach backwards ; but there are no traces 
of the nasofrontal, or nasomaxillary sutures. The middle of the under surface of each 
nasal bone presents a strong, rounded, longitudinal ridge, on each side of which there is 
an equally distinct concavity, and the apposed slightly thickened inner edges of the two 
nasal bones form a third, less marked, median ridge. The expanded upper edge of the 
perpendicular plate of the ethmoid embraces this middle ridge, while the nasal turbinal 
bones are continuous with the ridges on each side of it (Plate VI. fig. 1). 
A well-marked notch, or sinuosity, separates the upper from the lateral contour of 
the anterior nares ; and, about an inch below this, the inner surface of the outer wall of 
the nostril exhibits a rounded elevation or thickening. Still more inferiorly, the wall 
of the nasal cavity is somewhat excavated, so as to present a thin anterior edge, which 
passes into the trough-like lower boundary, constituted by the palatine portions of the 
prsemaxillse. These are separated throughout their whole length in the middle line 
(a distance of rather more than an inch) by a fissure less than one-tenth of an inch 
in diameter posteriorly, but twice as wide in front, the prsemaxillse becoming more 
