from the Shales of the Northumberland Coal-field. 267 
corresponds very well in form to the central portion of the 
fragmentary skull figured in the paper already referred to, by 
Prof. Huxley ; but in the new form it is less angulated. ‘The 
frontals, too, appear to be longer, though their anterior extre- 
mities are broken away; the post-frontals are arcuated in the 
same manner, but not to the same degree, forming the inner 
posterior boundary of the large orbits, and their connexions 
with the parietals and frontals are similar. The parietals 
widen Shears : and the foramen, which is situated in the 
line of the median suture, where there is an elongated emi- 
nence, is a little behind their centre, and is slightly lengthened 
in the antero-posterior direction. In the larger specimen it is 
one-fourth of an inch in length, in the other it is a little 
shorter. The occipital margin is concave, the epiotic bones 
projecting boldly backwards, and each terminating in a slightly 
ed, pointed, diverging horn or spine, about an inch long. 
In neither specimen are these horns (which are very similar to 
the “ postero-internal cornua” of Keraterpeton*) perfect ; but 
in the smaller individual the upper surface only is wanting. 
The external surface of the cranial shield is strongly sculp- 
tured in the usual manner observed in Labyrinthodonts ; that 
is, it is covered with anastomosing ridges separating pits and 
grooves ; but this peculiar ornament is not equally distributed: 
it radiates from the centre of the shield, where it is almost 
obliterated, and is strongest at the margins. Here the pits 
and grooves are deep and strongly defined. A rather wide 
rounded groove extends along the outer margin of the frontals, 
resembling the mucus-grooves of the Labyrinthodonts. 
The larger of these shields is seven inches long, including 
the posterior horns, and three and three-quarters inches wide. 
The other is six and one-quarter inches in length, and nearly 
three inches wide at the broadest part. Prof. Huxley estimates 
the width of the skull of Loxomma Allmanni, including the 
lateral portions, which are entirely wanting in our specimens 
of Pteroplax cornuta, at ten and three-quarters inches; and 
as it appears that the central portion, or that which cor- 
responds to the cranial shields above described, is about one- 
third the entire width, we are enabled to form an approximate 
estimate of the width of the skull of the new form, on the 
assumption that it had similar lateral cranial expansions. On 
this basis our new Labyrinthodont must have had a skull 
eleven and a quarter inches wide at the posterior or widest 
part; and, following up Prof. Huxley’s estimate, it could not 
be less than fifteen inches in length. If the body, therefore, 
* Trans. Royal Irish Academy, vol. xxiv., Science, p. 351, pl. 19. 
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