ESPECIALLY MYCTOPHOIDS 55 
the end of the palatine. Thus medial to the anterior end of the palatine the pre- 
maxilla extends backwards and appears to be associated with the anterior edge of 
the mesethmoid within the U-shaped indentation of the latter bone. The pre- 
maxilla extends posteriorly as a shallow lamina of bone bearing a single marginal 
row of teeth on its ventral edge. The teeth are small but recurved and have the 
same apical specialization as the palatine and ectopterygoid teeth. The maxilla 
appears to have entered the gape posteriorly and borne teeth along its ventral edge. 
Mandible. The mandible is shown in medial view in Text-figure 22. The 
mandible is long and shallow, although it has a considerable ventral extent lying in 
a horizontal plane. Anteriorly the mandible is acutely pointed and the symphysis 
is constricted. The dentary is the major component of the lower jaw forming the 
entire oral border as well as most of the lateral face of the mandible. Teeth are 
borne on the oral edge of the dentary and are numerous and clustered. All of the 
teeth are long and needle-like and similar to those on the ectopterygoid in being 
recurved. The articular facet is ill-defined, being somewhat less than a semicircle 
and with no retroarticular process posteriorly. The outer face of the mandible is 
smooth and bears no traces of ornamentation. 
Vertebral column. The vertebral column is shown in the restoration in Text- 
figure 23. It consists of approximately 70 vertebrae although the number is slightly 
variable, some specimens appearing to have up to 73, although none has less than 
70. Of these 70 or so vertebrae 30 are caudal. The centra are longest in the 
anterior precaudal region and decrease in length posteriorly, those of the caudal 
region being uniform in size with the length of each centrum just in excess of its 
depth. In the anteriormost precaudal region the centra are at least twice as 
long as deep. All of the centra are mesially constricted and in the precaudal 
region this is especially noticeable. The characteristic feature of the precaudal 
region is the possession of prominent laterally directed transverse processes on each 
centrum. On the first few precaudal centra the transverse processes are relatively 
short and broad based, and borne on the anterior region of each centrum. Pleural 
ribs appear to articulate with the undersurface of each transverse process. The 
size of the transverse processes Is constant back to about the zoth precaudal vertebra 
where they begin to elongate and incline slightly forwards. Thus while the centra 
decrease in length the transverse processes increase so that the longest transverse 
process, on the 35th precaudal vertebra, is just longer than the centrum supporting 
it. The transverse processes rapidly decrease in length and incline ventrally to fuse 
together and produce a haemal arch by the goth vertebrae. Neural arches occur on 
all the vertebrae and are long and low. The neural spines arising from the arches 
are abbreviated and insignificant anteriorly but become more prominent towards 
the caudal region. The neural spines are straight. The neural arches occupy the 
whole of the dorsal extent of the corresponding centra, the neural spines being 
produced from the posterior end of each arch. Haemal arches and spines charac- 
terise the caudal region. The haemal spines remain small and feeble but, unlike 
the neural spines, exhibit a marked posterior curvature. The pleural ribs which 
articulate with the transverse processes are long and thin and directed posteriorly, 
