WOODWARD : FOSSIL FISHES OF THE UPPER LIAS OF WHITBY. 327 
ethmoidal region (pi. xlvi,, fig. 1). The roof is flattened in the 
middle, but curves sharply downwards on either side ; and it slopes 
gradually with very little convexity from the occiput to the snout. 
The occipital border is overlapped by a single pair of supra- 
temporal plates (s. t.), which are somewhat fractured and displaced 
forwards in the fossil. They are transversely elongated and 
irregularly triangular in shape, and their acute apices meet in the 
middle line. Their external surface is smooth anteriorly, but 
marked by irregular tubercles and ridges, more or less radiating 
from the course of the transverse slime-canal in the hinder half. 
The parietal bones (pa.) form a very unsymmetrical pair, and their 
maximum extent equals at least one-third of the total length of the 
cranium. That of the left side is much the largest, the suture 
between the two elements being sharply diverted towards the right 
in front of an acute bend which occurs at the level of the transverse 
slime-canal. This canal is marked upon the bone on either side by 
a short groove, which is directly continuous with a similar groove on 
the squamosal bone (/.), and soon abruptly turns backwards at right 
angles to the occipital border. The external surface of the parietals 
is, for the most part, smooth, with mere traces of tubercles, and a 
few scattered small pits, probably for slime glands. The squamosals 
(sq.) are long and narrow, truncated behind and pointed in front; 
they do not extend so far backwards as the parietals, but reach a 
point quite as far forwards, and are thus partly in contact with the 
frontal on either side. Their external surface exhibits more ten- 
dency to rugosity than that of the parietals. The length of each 
frontal (Jr.) equals about two-and-a-half times its maximum width ; 
and this pair of bones meets in a very wavy median suture, which 
exhibits two sharp bends, and one slighter bend further forwards. 
The frontals taper considerably in front, while their middle and 
postero-lateral portions are marked with some rugosity. Their 
outer margin above each orbit is slightly excavated for the accom- 
modation of the upper plates of the circumorbital ring, which are 
partly shown, though much crushed and disturbed on both sides. 
These plates, so far as preserved, are more strongly ornamented with 
tubercles and short rugae than the cranial roof ; and three of the 
