ESPECIALLY MYCTOPHOIDS 49 
The maxilla is an elongated, stout bar of bone which is straight for most of its 
length except anteriorly where it is curved medially. The maxilla is smooth, un- 
ornamented and bears no traces of having been toothed. The premaxilla forms the 
anterior half of the oral border of the mouth and the maxilla enters the gape behind 
it. Anteriorly the maxilla lies in the oblique groove on the lateral face of the pala- 
tine, and the curved head of the maxilla is inflected towards the mid-line above the 
dorso-lateral surface of the palatine. The maxilla was attached to the premaxilla 
ligamentously. 
A small supramaxilla is present on the dorsal edge of the maxilla near to its hind 
end. The supramaxilla is elongated antero-posteriorly, markedly curved and orna- 
mented slightly with tuberculated ridges. 
Mandible. The mandible is shown in medial and lateral views in Text-figures 20 
and 21. It is long and relatively shallow, its maximum depth being less than one- 
fifth of its length, although there is a considerable horizontal extent to the mandible 
where the ventral edge is curved medially. Anteriorly the mandible tapers to the 
constricted symphysis. The dentary forms much of the mandible with upper and 
lower thickened regions joining anteriorly. The thickened dorsal limb bears 3 rows 
of teeth on its oral side. The extreme oral border bears a close series of minute 
teeth. Medial to this row there is a second row of larger teeth which are irregularly 
distributed and unevenly spaced. The internal teeth are the largest and there 
are approximately 7 in the row. The largest tooth is the second and tooth size 
decreases posteriorly. The teeth do not bear the post-apical barb so characteristic 
of the palato-pterygoid teeth, however they are laterally compressed with anterior 
and posterior cutting edges. All of the teeth in the three rows are conical, hollow, 
and firmly fused to the jaw by an unexpanded base. The largest teeth are more 
markedly recurved than the smaller ones. 
The articular forms the posterior mandibular region and is inserted on to the 
internal face of the dentary and occludes the posterior V-shaped indentation of the 
latter bone. The articular facet is shallow with a mesial ridge corresponding to the 
constricted condyle. There is no retroarticular process behind the articular facet so 
that the facet is vaguely defined. Beneath the facet, on the lateral face of the 
articular, traces of a groove are present in which the mandibular sensory canal ran. 
The canal was continued in a ventro-lateral groove along the surface of both the 
articular and the dentary. Ventrally the mandible is considerably thickened and 
ornamented by prominent longitudinal bony ridges extending forwards from 
beneath the articular facet, and backwards from the symphysial region on the 
dentary. The remainder of the lateral face of the mandible is smooth except for the 
oral border of the dentary where a narrow band of longitudinal ridging is observed. 
A minute angular element is visible on the extreme postero-ventral angle of the 
mandible. 
Body. The vertebral column is estimated to consist of approximately 60 verte- 
brae (50 are shown in B.M.N.H. specimen number 38113). Of these approxi- 
mately 30-32 are caudal. The precaudal vertebrae bear long narrow ribs supported 
on small transverse processes. The ribs extend laterally around the abdominal 
