ESPECIALLY MYCTOPHOIDS 81 
f. mes.vo 
pal.t 
ecp.t 
den.t 
6 
g.sym 
q b.md.V 
10mm 
art 
Fic. 36. Enchodus lewesiensis (Mantell). Hyopalatine bones and mandible of the 
left side in medial view. 
pterygoid expands medially in front of the endopterygoid, so that both sides of 
the V-shaped trough are formed of ectopterygoid. The trough widens anteriorly 
into a U-shape, and the postero-ventral region of the palatine rests within it. 
On the ventro-lateral region of the palatine bone there is a longitudinal ridge pro- 
jecting laterally and ventrally. The ectopterygoid spreads anteriorly, ventral to 
this ridge and articulates with its undersurface. Ventrally the ectopterygoid 
bears a row of large teeth which decrease in size posteriorly. The anteriormost 
ectopterygoid tooth arises from the ventral edge of the bone. Farther back along 
the ectopterygoid, the endopterygoid projects below the suture line between the 
two bones so that the more posterior teeth of the ectopterygoid series tend to arise 
from the ventro-lateral surface. The bases of the teeth are angled in such a manner 
as to make the main body of each tooth hang vertically downwards. There are 
approximately 7 functional teeth present on the ectopterygoid at any one time, and 
replacement teeth are visible close to the functional ones. All of the teeth are 
elongated and needle-like with well defined, but not particularly expanded bases. 
The teeth are laterally compressed to give rise to two cutting edges which are not 
strictly anterior and posterior, but set somewhat obliquely to the long axis of the 
ectopterygoid, and have a slightly recurved aspect. 
- The endopterygoid is visible from the lateral aspect as a small strip of bone below 
the region of fusion with the ectopterygoid. The endopterygoid bears a marginal 
row of minute teeth. On the internal face of the endopterygoid several more rows 
of minute teeth are seen radiating forwards and upwards. The more dorsal region of 
the endopterygoid inclines medially where it forms the roof of the mouth. 
The palatines are characteristically shaped and composed of dense bone. The 
characteristic feature is the possession of a single, enlarged, terminal tooth. This 
