186 
ACTINOPTEBYGII. 
impression of the external aspect of the roof on the other 
side of the fossil, this bone is not exposed above. The 
parietals (p«.) are an unsymmetrical pair of plates, 
broader than long, meeting throughout their length in 
a slightly sigmoidal suture, and marked by about two 
ridges which extend from border to border, w^hile other 
short ridges and tubercles are observed behind. The 
squamosals (sq.) seem to have been very narrow and 
insignificant plates at the postero-lateral angles of the 
skull, not extending further forwards than the parietals. 
The frontals (fr.) extend and expand backwards to form 
more than half the postorbital region of the cranial roof ; 
and these are not a symmetrical pair, that of the right 
side being wider and extending further backwards than 
that of the left side. The few ornamental ridges on these 
bones do not quite reach the hinder margin and are in no 
way connected or correlated with those on the parietals. 
The very narrow interorbital region is comj)aratively 
stout, and impressions suggest that a delicate crescent- 
shaped wing extended upwards and outwards from the 
frontal on each side to protect the relatively large eye¬ 
ball. The anterior end of the frontals seems to have 
expanded a little again on the rostral region, two wings 
of membrane-bone being crushed iu the fossil on the sides 
of the ethmoid and these are apparently directly con¬ 
tinuous with the frontals. The orbit (orb.) occupies one 
quarter of the length of the skull, and at its anterior 
border on each side there is a thin, ovoid, convex plate, 
which seems to be a dermal or membrane-bone. The 
well-ossified mesethmoid (eth.) is marked by numerous 
fine longitudinal ridges terminating a little behind the 
anterior end, which is scarcely expanded but is curiously 
truncated and hollowed in front in such a way as to give 
it the appearance of being a tube. The crushed jaw¬ 
bones lie on either side of the rostral region, and extend 
for a short distance in advance of it, tapering to an acute 
point. The bases of a single regular close series of minute 
teeth in the dentary are observable on the left side. Im¬ 
mediately behind the occiput, and pointing to its median 
re-entering angle, the pair of post-temporal plates (p.t.) 
is preserved; each being triangular in shape, longer than 
broad, and unornamented on its outer face. Just behind 
these again is one of the narrow heart-shaped scutes, 
