52 ON THE-SPHENOID, CRANIAL BONES, OPERCULUM, 
than the sphenoid of Ceratodus, ao possesses ae | 
mental contormation. This bone was first pene ivy Ve Mesiate: 
Hancock & Atthey in the “ Trinehotionie” I have : 
occasion to refer to, in a paper entitled “ A few remarks on 
Dipterus and Ctenodus, and on their relationship to Ceratodus 
Forsteri, Krefft” ; but they did not give any illustrations. Mr. ; 
arkas, F.G.S., in his “ Coal Measure Palzontology,” q 
merely mentions the fact of some sphenoid bones being in his ‘4 
ssion, and portrays one in an excellent lithograph. Messrs. 4 
rae & Atthey thus describe the bone in the paper mentioned ' 
above :—* Thé sphenoid is a much elongated depressed bone, with 
Wile a expansion near the anterior extremity ; in ; 
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ining to o conical at the extremity, and fits in between the 
aoe bones that support the dental plates. The lozenge- 
ormed expansion lies partly behind these bones ; and t 
a considerable distance further : e large species for 
nearly five inches. * The basi-sphenoid at its junction — 
with the lozenge-formed e expansion is usually thick ast nearly ; 
circular ; elsewhere it is flattened.” A specimen in my cabinet 2 
point Oe rises into a hgh erest on the buccal surface. I n en 
also in my specimen a point not mentioned by Messrs. Hancsel 
& Atthey, and it is that on each edge just posterior to the lateral 
swelling in centre of the basi-sphenoid is a small oval ed pe 
jike the pee rpc of an articulation, and I am inclined to 
sider that it is the remains of a joint between this bone and "thi 
first rib, jane as we see is the case in Ceratodus. I am not aware 
that the rib has ever been discovered in situ, but pana would 
one to infer that my conjecture is correct. For 
cavities are im' It is > ae 
ar me to add that the hedtae oiiie extension of 
