from the Shales of the Northumberland Coal-field. 355 
has been carefully removed from the upperside of the large 
sphenoid bone of this species by which the size of the fish 
was estimated. And now this interesting specimen reveals to 
us the cranial bones of the occipital region in an undisturbed 
and excellent state of preservation. ‘The whole of the bones 
of one side are almost perfect; so that there is no difficulty in 
restoring this portion of the cranium, the constituent bones of 
which are arranged exactly as they are in the figure of the 
“cranial buckler” of Dipterus given by Hugh Miller in his 
‘ Footprints of the Creator.’ 
The bones vary little in size, and, with the exception of the 
central occipital and parietals, are mostly irregularly penta- 
gonal. There are three occipitals: the central one is not much 
larger than the lateral; the former is nearly as wide as it is 
long, and is seven-sided, with the anterior margin a little 
inted in the centre, and the posterior margin nearly straight. 
‘he lateral occipitals are connected with the postero-lateral 
margins of the central occipital, and, diverging in front, admit 
a bone on each side, which is wedged in between them and 
the antero-lateral borders of the central occipital and the ex- 
ternal margins of the parietals. Hxternal to these bones, and 
in connexion with their outer margins, are three other bones, 
which form the lateral borders of the cranium. In all there 
are five bones on each side of the central occipital and poste- 
rior part of the parietals. ne a small portion of the left 
parietal is preserved ; but enough is present to show that this 
a of bones are elongated, being widest apparently a little be- 
ind their centre, and having their posterior margins slightl 
divergent to receive the anterior angle of the central poe | 
The surface of the bones is not ornamented with “ waved 
and bent lines,” as those of Dipterus are described to be by 
Miller (2b¢d. p. 61), but is minutely granulated and punctate, 
similar to that of the opercles described in the paper on Cte- 
nodus already referred to, and here and there are indications 
of the radial bone-structure beneath. 
The original estimate of the width of this head was nine 
inches. It is now evident that it really was eight and a half 
“Inches across the occipital region, without taking into account 
a fragmentary bone, probably a portion of an operculum. 
Were this added to the above measurement, the width would 
be ten inches. 
The external characters of the palatal plates of the various 
species of Ctenodus were ieactber in the paper on that genus 
mentioned above. Nothing, however, was said of the internal 
structure, such matters of detail having been reserved for some 
future occasion. But it is now perhaps desirable to give some 
