ESPECIALLY MYCTOPHOIDS 149 
medial edge of the ectopterygoid, lying in the roof of the mouth associated with the 
ventro-lateral flange of the parasphenoid. Anteriorly the palatine articulation with 
the mesethmod region of the skull is unexpanded. The lateral ethmoid contacts 
the postero-dorsal surface of the palatine. The palato-pterygoid bar bears a 
continuous, single series of teeth along its entire length. 
Fic. 67. Hemisaurida hakelensis sp. nov. Restoration of the skull in lateral view. 
Dermal upper Jaw. The dermal upper jaw is shown in lateral view in Text-figure 
67. The premaxilla is elongate and very shallow with no ascending process. 
Anteriorly the premaxilla is slightly expanded and wrapped around the snout. The 
premaxilla forms approximately the anterior half of the oral border of the upper jaw, 
and supports a fringe of minute teeth. The maxilla is almost twice as long as the 
premaxilla and is narrow along its entire length. It enters the oral border of 
the jaw behind the premaxilla and bears teeth on its ventral edge. The maxillary 
teeth are more prominent than those on the premaxilla and increase in size poster- 
iorly, where they are forwardly inclined. At its extreme anterior end the head of 
the maxilla curves in towards the mid-line and bears a medial facet which is asso- 
ciated with the dorsal palatine surface. Above the maxilla is a long, low supra- 
maxilla which just extends beyond the posterior end of the maxilla. 
Mandible. The mandible is shown in lateral view in Text-figure 67. It is long, 
shallow and formed mostly of dentary. The articular facet is shallow and not well 
demarcated and there is no retroarticular process. The lateral face of the articular 
has a flange passing forwards horizontally from the articular facet. The groove and 
shelf produced above this flange support the maxilla and supramaxilla when the 
jaws are closed. The oral margin of the dentary has a series of small, clustered 
teeth. 
Opercular bones. The opercular bones are shown in lateral view in Text-figure 
67. The preoperculum is deep and narrow and curves forwards ventrally. Postero- 
ventrally it is produced into a prominent acutely pointed spine. The tube which 
contained the preopercular sensory canal traverses the entire length of the pre- 
operculum and opens ventrally behind the condyle. The operculum is a very large 
