46 PROFESSOR HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 
convex inwards and concave outwards, and its inferior edge becomes much thickened as 
it curves outwards. It is attached to the maxilla by an anterior and superior thin, and 
a posterior and inferior, much thicker, plate of bone. Three passages, consequently, lie 
between the lateral walls of the nasal chamber and the ‘ scrolls ’ of the inferior turbinal, — 
an upper, long, narrow, and flattened from side to side ; a middle, reniform in section ; 
and an inferior, rounded in contour. The ridges upon the under surfaces of the nasal 
bones are continued, as I have stated above, into two thick plates of lamellated bone 
(Plate VI. fig. 1, c), which increase in depth from before backwards and pass into what 
are, probably, the superior ethmoidal turbinals. Their inner surfaces are flattened 
and parallel with the sides of the perpendicular plate of the ethmoid. Their outer 
surfaces, irregularly concave, are separated by but a narrow interval from the concave 
faces of the superior scrolls of the inferior turbinal bone. 
The posterior view of this fragmentary skull (Plate VI. fig. 2) affords a further insight 
into the arrangement of the bones which contribute to the formation of the olfactory 
chambers. The aspect presented is that of a transverse section taken just in front of the 
anterior end of the cranial cavity. The comparatively thin posterior part of the lamina 
jperpendicularis of the ethmoid (Fth) is seen abutting, above, against the frontal bones 
(Fr), and, below, becoming connected with the vomer (Vo), the posterior nearly straight 
free edge of which bone ends on the floor of the nostrils, at the level of the posterior 
margin of the third molar tooth, and thence slopes obliquely upwards and backwards. 
The ethmovomerine plate, however, is not free from all lateral' connexion with the tur- 
binal bones, as is commonly the case ; but a thin plate of bone, convex forwards and 
concave backwards, passes, on each side, from the vomer and the lamina perpendicularis 
to the lateral masses of the ethmoid. The inner surfaces of these are marked by broad 
flattened grooves, directed forwards and downwards, and separated by sharp ridges, which, 
in the recent state, were probably produced into delicate plates of bone. 
The lower portion of the lateral mass of the ethmoid, which represents the middle 
turbinal, is continuous with the inferior turbinal. The upper portion, representing the 
superior turbinal, is similarly continuous with the nasal turbinal. The superior tur- 
binal of each side forms the floor of a considerable cavity (Plate VI. fig. 2), which is 
walled in, externally and above, by the frontal bone, and represents a frontal sinus. A 
rounded dome (a) of bone projects backwards from the anterior wall of this cavity, 
which appears to communicate with the nasal fossse only by a few foramina, situated 
around the margins of the dome. 
The palate (Plate IV. fig. 3) is singularly narrow, seeing that its length, measured in 
a straight line, is about 9^ inches, while its width, between the outer edges of the 
alveoli, nowhere exceeds 3 inches. The longitudinal contour of the palate is concave 
anteriorly, convex posteriorly (Plate V. fig. 1). The crown of the arch of the anterior 
concave portion is opposite the hinder margin of the third alveolus ; from thence the 
roof of the palate slopes, downwards and forwards, to the free premaxillary edge. From 
the same point it slopes, downwards and backwards, to the level of the hinder margin 
