PEOFESSOE HUXLEY ON THE OSTEOLOG-Y OF THE GENUS GLYPTODON. 45 
distant by the divarication of their anterior and internal angles. The thick and rough 
anterior edges of the preemaxillee diverge obliquely from one another, both forwards and 
outwards and upwards and outwards, at a very obtuse angle, the interval between their 
anterior and external terminations amounting to 1-5 inch (Plate IV. fig. 3). Viewed 
laterally, the anterior ends of the nasal bones are seen to project about half an inch 
beyond the upper part of the lateral boundary of the nares, which slopes upwards and 
backwards with a slight forward concavity from the palatine portion of the preemaxilla 
(Plate V. fig. 1). 
The nasal cavity is divided, longitudinally, by a very strong osseous septum, which 
extends to the posterior end of the premaxillary fissure below, and to within 0 - 4 inch of 
the anterior contour of the nasal bones above (Plate VI. fig. 1). This septum terminates, 
in front and below, in a thin jagged edge; but above, it expands into a broad plate 
T2 inch wide, presenting a deep and broad notch above, into which, as I have previously 
stated, the conjoined median edges of the nasal bones are received. The septum is about 
2'6 inches high in front; and of this height 2-2 inches, or about five-sixths, is formed by 
the perpendicular plate of the ethmoid, while the rest belongs to the vomer (Vo.). The 
ethmoidal plate is thin in front, thicker in the middle, and thin again posteriorly. The 
lower half is somewhat excavated on each side, from above downwards ; it ends in an 
inferior edge, or rather surface, 0-7 inch in diameter, anchylosed with the upper edge of 
the vomer, which has, in front, a corresponding thickness. The floor of the anterior 
part of the nasal cavity (i. e. as far as the level of the fourth alveolus) is concave from 
side to side, and convex from before backwards, its convexity corresponding with, but 
being much more strongly marked than, the concavity of the arched roof of the palate. 
At about 2 inches from the anterior boundary, a sharp longitudinal ridge commences 
upon the floor of each division of the nasal cavity, and extends backwards, for a distance 
of about 1| inch, to the summit of the arch formed by that floor (Plate VI. fig. 1, a). 
Each ridge has a sloping convex external face, and a perpendicular concave inner face, 
0-2 inch high. Between the latter and the side of the vomer, which is excavated for a 
corresponding distance from above downwards, lies a canal, a quarter of an inch wide, 
and open above and at its ends. The- floor of each nasal chamber rises gradually into 
its lateral wall ; and upon this, about three-fourths of an inch from the floor, appears a 
ridge which, at about an inch from the antero-lateral margin of the nostril (or just above 
the anterior end of the ridge on its floor), passes backwards into the commencement of 
the inferior spongy bone (Plate VI. fig. 1, b ). The root of attachment of this bone to 
the maxilla is, as usual, a narrow and thin, though long, bony plate, which on its free, 
or inner, side is continued into two scroll-like lamellae, an upper and a lower. The 
upper scroll comes much further forward than the lower, and is a stout plate of bone, 
slightly concave inwards and convex outwards. In front, it ends in a thin free edge. 
Superiorly, its margin is folded over outwards, and becomes anchylosed with the lateral 
wall of the nasal chamber. 
The inferior lamella commences about an inch behind the superior one. It is thick, 
