ON CARBONIFEROUS LABYRINTHODONTS 531 
posing this fragment of a skull are, for the most part, distinctly 
traceable, and prove it to be composed of two quadrate, supraoccipital 
elements with two elongated parietal bones, the apposed edges of 
which are deeply notched at the junction of their middle with their 
posterior third, so as to give rise to a rounded parietal foramen, 
yoths of an inch wide. The parietals unite, in front, with a pair 
of frontals which are narrow behind, but expand anteriorly, and 
then become broken and disfigured. An arcuated postfrontal is 
connected with the posterior moiety of the outer edge of each frontal, 
and with the antero-external edge of the parietal. Externally, its 
smooth, almost vertically bevelled, margin bounds the inner and 
posterior part of the orbit. The latter cavity has an irregularly oval 
shape, the long axis of the oval being directed, from without and in 
front, obliquely inwards and backwards, at an angle of about 45° 
with the long axis of the skull. The anterior and outer part of the 
wall of the orbit is broken away ; but, internally, it is bounded by a 
stout prefrontal, on the under face of which is the indication of a 
ridge, now broken away, but which once projected towards the palate. 
The prefrontal joins the postfrontal and, just in front of the junc- 
tion, expands, somewhat suddenly, outwards, so as to form a sort of 
promontory which disturbs the even contour of the orbit on its inner 
side. 
The postero-lateral boundary of the orbit is formed, in its hinder 
half, by a postorbital bone, and, in its anterior half, by what appears 
to be the jugal bone. All that remains of the outer boundary is a 
trihedral bar of bone 0’5 inch wide, which I take to be the hinder 
part of the maxilla, though it may be the continuation, forwards, of 
the jugal. This bony bar is concave on its outer or upper surface, 
which is coarsely sculptured, while its inner and outer surfaces slope 
towards one another, so as to form an edge below, which is sharp in 
front and gradually dies away behind. The outer face is flat, and 
exhibits a delicate rugose sculpture: the inner is slightly excavated. 
Behind the orbit the lateral part of the roof of the cranium widens, 
and is produced, at its external and posterior angle, into a broad, 
expanded, and irregularly shaped plate, whose extreme outer point 
is broken away. In consequence of the projection of this plate 
beyond the general contour of the skull, the lateral margin of the 
latter curves suddenly outwards, midway between the orbit and the 
postero-lateral extremity, and then passes into the straight outer edge 
of the plate in question. This plate appears to be mainly formed by 
the quadrate and squamosal bones. Internally it presents a curved 
contour, convex inwards, which sweeps round when it reaches the 
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