564. CARBONIFEROUS LABYRINTHODONT 
opposite side may have been developed. If the sinus upon the 
palatine alveolar plate of the opposite side has the same signification, 
it would appear as if there were normally two great palatine tusks on 
each side, but that the anterior and posterior of opposite sides are 
shed simultaneously. 
The fossil was broken into two pieces when it reached me; the 
fracture passing obliquely between the third and fourth teeth on the 
left side, and through the fourth on the right. The fractured surface 
shows the roof of the skull, or rather the snout, and proves that it was 
raised into a broad longitudinal ridge, so convex as to be almost 
semicircular, about 1°5 inch broad and o°6 inch above the general level 
of the facial bones. From the sides of this convexity, the sides of the 
face slope with a gradual curve towards the alveolar margin. The 
depth of the skull, immediately over the centre of the maxillary 
alveoli,is rather less than one inch. From the centre of a line joining 
the margins of the alveoli to the top of the central ridge is a distance 
of about 1'9 inch ; and in the occipital region the skull is not deeper: 
considering its breadth and length, therefore, the skull is extremely 
flat. 
The teeth are round, or slightly oval in section at their bases, and 
throughout the greater part of their length. They taper gradually to 
sharp points and become slightly incurved towards their apices. 
Their bases are not grooved, but, on the contrary, are marked by 
numerous delicate and sharp longitudinal ridges, so that transverse 
sections appear to be very slightly polygonal. Towards the apex of 
the tooth, two of these ridges, an anterior and a posterior, become 
more distinctly marked, and, combined with a very slight flattening of 
the tooth, give it a double edge. 
In one of the anterior teeth, the front face towards the point is 
much worn, as if by attrition against one of the mandibular teeth. 
Transparent transverse sections of the teeth exhibit a singularly 
beautiful and complex structure. The relatively small pulp-cavity 
sends off primary radiating prolongations, which pass straight to the 
circumference of the tooth, and at a small distance from it terminate 
by dividing, usually, into two short branches, each of which gives off 
from its extremity a wedge-shaped pencil of coarse dentinal tubuli. 
These spread out from one another, and terminate in a structureless 
or granular layer, which forms the peripheral portion of the dentine, 
and, from the small irregular cavities scattered here and there through 
its substance, reminds one of the ‘globular dentine’ of the human 
tooth. An extension of this peripheral layer is continued towards 
the centre of the tooth, between every pair of primary prolongations 
