ESPECIALLY MYCTOPHOIDS 53 
shallow and widest at the hind end of the orbits. The frontals make up practically 
all of the skull-roof reaching back almost to the occipital border. Anteriorly the 
frontals taper to contact the rear edge of the mesethmoid near to the front end of 
the snout. The frontals widen to form the upper margin of the orbits. Posteriorly 
the frontals contact the supraoccipital and the parietals. The ornamentation on 
the frontals radiates in all directions from the centre of ossification above the rear 
end of the orbit. Rows of minute tubercles pass anteriorly and antero-laterally 
above the orbit, and posteriorly and postero-medially above the cranial cavity itself. 
Towards the lateral edge of the frontal above the orbit the ornamentation is no 
longer in uniform rows but is randomly scattered. The supraoccipital is small, 
meeting the frontals anteriorly and forming the centre of the occipital border 
of the skull-roof. The parietals lie lateral to the supraoccipital and are small 
transversely orientated bones ornamented with tubercles. The pterotic forms the 
postero-lateral border of the skull-roof, and the rows of tubercles on its dorsal 
surface originate near the hind end of the bone. The sphenotic projects laterally 
from beneath the frontal at the rear end of the orbit, but its dorsal surface appears 
to have been unornamented. 
The mesethmoid is in the form of two strips of bone joined anteriorly. These 
strips flank the extreme anterior ends of the frontals. The mesethmoid is slightly 
expanded anteriorly into two small lateral wings and bears a median, anterior, 
U-shaped indentation which imparts a slight bifid appearance. The vomer corres- 
ponds to the mesethmoid anteriorly in the possession of lateral wings. The wings 
are flattened and lie in a horizontal plane and fit into antero-posteriorly elongated 
facets on the antero-medial faces of the palatine. The vomer only meets the 
mesethmoid in this anterior region, widening behind to pass back as a prominent 
flattened plate which attaches to the parasphenoid. Teeth do not appear to have 
been present on the vomer. The parasphenoid is a straight rod of bone running 
through the base of the orbit, apparently without lateral flanges. 
Hyopalatine bones. The hyopalatine bones are shown in medial view in Text- 
figure 22. The jaws are elongate and bear a prominent armature of long teeth. 
The palatine bone is long and narrow, and in the form of a curved, thickened lamina 
with a longitudinal ventral concavity housing the teeth. In the extreme anterior 
region the bone narrows and the concavity is lost. The medial face of the palatine 
is excavated producing a facet for the reception of the lateral wing of the meseth- 
moid. Anteriorly the palatine ends in advance of the mesethmoid, and posteriorly 
below the anterior region of the orbit. The lateral ethmoid is not prominent and 
ventrally is weakly associated with the posterior end of the palatine. The teeth 
are closely packed and give the appearance of having been arranged in three major 
rows. The teeth are all of the same type, there being minor variations in length 
and breadth, but all are needle-like with unexpanded basal regions. The diameter 
of the tooth bases varies little between the large teeth and the small teeth, the major 
change in dimension is in the length. All of the teeth are hollow and oval in cross- 
section. The cutting edge of each tooth is confined to the extreme apex where the 
hollow cavity is occluded and the cross-section of the tooth becomes more elliptical. 
