54 ON THE SPHENOID, CRANIAL BONES, OPERCULUM, 
Mr. a. may rhe correct enough in his statement, if I may 
Mr. Atthe 
. taking the nomenclature of Pander, Mr. pakke that of ian 
On a slab in my possession are two masses of head-bones, oe 
on each surface, as though they had originally been united i 
one shield, and before fossilization some catastrophe ha i 
pened and bent the roof of the cual ee the middle, but 
whether this is so or not, the two masses are certainly head- 
bones of Céenodus, as they present the pitted and emule —< 
ane in the Ceratodus’ skull, but this latter fact may arise from 
the fragmentary nature of my specimens. By comparing one of | 
my specimens with Mr. Barkas’s figure pl. x, fig, 244, however, I 
ecespital; median occipital, epiotic, parietal. ther ent 
a cranium there isa bone wi re an arrow a projection pire 
may corrompond d with Mr. ’s occipital, which is thus 
age and has a wedge-shaped. process in the centre.” 
supra-occipital, epiotic, and median s. It must nik be 
ten that in these names I am onl se i conjecture. 
In all the erania that ha have been ie rape the o urface of 
me 0: ne i 
distinct as see te long depressed arborescent streaks are 
the bone, the surface thus having a peculiar d aspect, and 
om one the impression of a cartilage sian become fossilized 
was advancing; a microscopical examination, how- 
ever, shows, that the bone is osseous throughout. The bones are 
always small compared with the size of the cranium; vary muc 
in “again but in size they are pretty uniform, no bone predomi- 
uch over the others; they unite te with each other by 
fuilicteatod sutures that have ve appatently become anchylosed early 
=e ife to ate hy com) shield. ee 
reula are of comparativel: uent occurrence in 
dees aie the N Northumberland coal —— They vary greatly 
