ESPECIALLY MYCTOPHOIDS 89 
posteriorly and terminates just behind the end of the lachrymal, forming the 
anterior half of the oral margin of the upper jaw. There is a single marginal row of 
teeth which are small, acutely pointed and fused directly to the bone with no 
evidence of a tooth base. The teeth are evenly spaced and decrease in size posteriorly 
where they appear to be no more than an extension of the tubercular ornamentation. 
The maxilla is an elongate, uniformly narrow strut of bone, entering the gape 
posteriorly. The head of the maxilla lies in a groove on the dorso-lateral surface of 
the palatine. The anterior region of the maxilla, behind the head, bears a small 
lateral flange under which the postero-dorsal edge of the premaxilla fitted. This 
flange tapers posteriorly to merge with the main shaft of the maxilla behind the 
premaxilla. The ornamentation of the maxilla is in the form of minute tubercles, 
which begin as two rows on the lateral flange and continue back as three rows along 
the remainder of the maxilla. The maxilla expands slightly towards its extreme 
posterior end and is laterally compressed where it rests against the lateral face of the 
mandible. 
Mandible. The mandible is shown in lateral view in Text-figure 39. It is long 
and deep, but the depth is greatly reduced at the symphysis. The dentary is the 
largest component, forming the whole of the upper border, the anterior two-thirds 
of the lower border, and approximately half of the lateral face of the jaw. Internally 
the dentary gives rise to a tooth-bearing flange on the oral margin. This flange 
bears a single row of evenly spaced, relatively large, acutely pointed teeth, confined 
to the anterior two-thirds of the length of the jaw. The teeth are about 8 in number, 
laterally compressed, and decrease in size posteriorly. At the symphysis the 
anteriormost tooth is approximately twice as long as any of the other teeth in the 
row. Immediately in front of this tooth, at the extreme symphysial end, are two 
smaller teeth which are about one-quarter of the length of the longest tooth. All of 
the teeth are, however, identical in other respects. A second row of teeth is present 
on the extreme oral margin of the mandible, composed of between 30 and 40 small, 
pointed, laterally compressed teeth decreasing in size posteriorly. 
The facet on the articular is deeply concave. The anterior edge of the facet is 
rolled upwards around the condyle, whilst posteriorly a short retroarticular process 
curves around behind the condyle. Postero-dorsally the articular is noticeably 
thickened. It joins the posterior end of the oral margin of the dentary to produce 
the coronoid process. The articular extends anteriorly to form the posterior region 
of the lateral face of the mandible. 
The angular is a very small slip of bone on the postero-ventral angle of the jaw, 
below the articulatory facet. 
The mandibular sensory canal ran along the ventro-lateral part of both the 
articular and the dentary. This canal entered the articular through a pore in the 
lateral face of the retroarticular process and passed within a tube of bone beneath 
the articular facet. Anteriorly the sensory canal continued forwards in a shallow 
groove in the dentary. The lateral face of the mandible is ornamented most 
markedly at either end of the jaw. The tubercles on the dentary radiate backwards 
from the symphysis, and on the articular forwards from below the facet. 
