SEMIOXOTIDiE. 
79 
ascending process which fits into a groove on the inferior aspect of 
the frontal bones. The base of the cranium is sheathed by a great 
parasphenoid hone and by the coalesced dentigerous vomers. The 
parasphenoid is narrowest at the origin of the large fan-shaped 
basipterygoid processes, expanding much behind and exhibiting a 
deep cleft in its hinder margin. It bears no teeth and is pierced 
mesially by a foramen for the passage of the internal carotids, 
which appears single on the lower face, hut double on emerging 
above; the superior or attached face also shows the deep excavation 
forming the floor of the basicranial canal. The vomer is a stout 
thickened bone with crushing teeth, showing cavities in which the 
germ-teeth are formed; and the dentigerous hones of the palato- 
pterygoid arcade, closely connected with the vomer in front, exhibit 
a similar thickening. The hyomandibular is an elongated, laterally 
compressed hone, with its long axis slightly bent at the origin 
of the process of support for the operculum. It is somewhat 
strengthened by longitudinal ridges on the outer face, and the 
surface for attachment with the cranium is much extended. The 
hone is not pierced by any foramen. The symplectic element 
remains unknown, hut the hinder border of the quadrate exhibits 
an inner surface evidently for union with it. The quadrate is 
slender for a fish with so powerful a dentition, and in the fine 
example of Lepidotus latifrons from the Oxford Clay (no. P. 6841) 
this element is of much interest as exhibiting a very different degree 
of ossification on the two sides. The metapterygoid bone is also 
comparatively delicate, but it shows a broad facette on its upward 
and anteriorly directed process, which may have articulated with 
some lateral element of the cranium. The hinder portion of 
Meckel’s cartilage is ossified as a robust articular bone, and to its 
outer face there is apposed a large plate, probably to be interpreted 
as angular. The coronoid region of the mandible is very deep, and 
the summit of the elevation is completed by a very small coronoid 
bone, shown in a Wealden specimen of L. manlelli (no. P. 6342). 
The dentary bone, very deep in the coronoid region, becomes much 
narrower in its tooth-bearing portion ; and its anterior half curves 
rapidly inwards to meet its fellow of the opposite side in a somewhat 
deepened symphysis. To the inner side of the dentary bone the 
robust spienial is articulated by a roughened face, and it also enters 
the mandibular symphysis ; whereas the dentary exhibits only one 
regular series of teeth, this element has several irregular series of 
a more tritoral character. The ceratohyal exhibits its ordinary 
hour-glass-shaped form, and is deepest behind. The hypohyals are 
a pair of very small triangular bones; and no evidence of an ossified 
glossohyal has hitherto been observed. 
