ESPECIALLY MYCTOPHOIDS 181 
The parietals are bordered anteriorly by the frontals and posteriorly by the 
epiotics. The parietal is smooth apart from two small strips of ornamented bone 
fused to the surface. One of these strips is transversely arranged, the second 
longitudinally. Both the transverse and longitudinal strips contain partially roofed 
dorsal grooves. These two strips of bone represent the remains of a supratemporal 
bone, and housed the supratemporal sensory canal. 
The pterotic forms the postero-lateral border of the skull-roof contacting the 
sphenotic anteriorly and the frontal medially. Postero-medially it is separated 
from the parietal and the epiotic by an indentation of the posterior edge of the skull- 
roof. This indentation is in the form of a narrow antero-posteriorly orientated 
groove, probably representing the upper region of the opening to a roofed post- 
temporal fossa. The dorsal surface of the pterotic is ornamented with irregular, 
tuberculated ridges. A tube is present within the pterotic opening anteriorly about 
mid-way along the bone, and posteriorly in two places. The first of these posterior 
openings is positioned on the edge of the pterotic and the second on the inner edge 
of the posterior part of the pterotic. On the lateral face of the neurocranium the 
pterotic makes up the major part of the hyomandibular facet. Above the hyo- 
mandibular facet the pterotic contributes towards the formation of the dilatator 
fossa which is an elongated oval fenestra. 
The sphenotic projects laterally from beneath the frontal at the rear of the orbit. 
Dorsally the sphenotic joins the pterotic posteriorly, and is unornamented. 
Laterally the sphenotic gives rise to a stout strut passing ventro-medially to contact 
a corresponding strut of the prootic. Between these two struts a cup-shaped recess 
is produced and this forms the anterior region of the hyomandibular facet. 
The course of the sensory canals is indicated both by tubes within the bone and 
open grooves on the surface. The supraorbital sensory canal was confined to the 
frontal, and opened anteriorly on the edge of the frontal in advance of the orbit : 
no trace of nasal bones was found in this region. Posteriorly the sensory canal 
passed postero-medially from the centre of ossification. The infraorbital sensory 
canal passed across the dorsal surface of the sphenotic and under the lateral extension 
of the frontal. The lateral line canal from the post-temporal appears to have 
divided before entering the posterior part of the neurocranium. The otic branch 
of the infraorbital canal entered the pterotic above the post-temporal fossa and 
passed forwards within the bone. Anteriorly the otic branch passed on to the 
dorsal surface of the sphenotic beneath the frontal to contact the main infraorbital 
canal. The supratemporal sensory canal is the second division of the main lateral 
line canal, and passed medially on to the surfaces of both of the limbs of the supra- 
temporal. The supratemporal canal appears to have been continuous across the 
dorsal surface of both the parietals and the supraoccipital. The preopercular 
sensory canal was transmitted through a postero-lateral pore of the pterotic and 
joined the otic branch of the infraorbital canal within the pterotic. 
The epiotics form part of the occipital border and the medial edge of the posterior 
part of the post-temporal fossa. The major portion of the epiotic is on the posterior 
face of the neurocranium. Postero-dorsally the epiotic gives rise to a smooth, 
