or THE VOMEE, ETHMOID, AHD INTEEMAXILLAET BONES. 
303 
extends back the whole length of the palate. The intermaxillaries prolong the vome- 
rine groove for a greater or less distance according to the genus. The distinctness of the 
central plate of the ethmoid from the vomer is very clearly seen, inasmuch as the former 
terminates abruptly where it becomes continuous with the cartilage in front, while the 
grooved surface of the latter is continued smoothly forwards. In vertical sections of 
skulls of the Dolphin and Grampus in the Museum of this University, although many 
sutures are obliterated, a straight line passing forwards from the inferior margin of the 
presphenoid indicates distinctly the place of contact of the still separate vomer and 
central plate of the ethmoid (fig. 25). The olfactory apparatus and lateral masses of the 
ethmoid are entirely absent ; but the posterior parts of the alee of the vomer are enor- 
mously expanded to take their place, and pass up on each side of the central plate of 
the ethmoid in front of the frontals, even as far as the nasals, forming the whole poste- 
rior wall of the nares, viz. the whole of that wall which in other Mammals is formed by 
the ethmoid. I notice also in Deductor glohiceps that the expanded margin of the vomer, 
with the assistance of an angle of the maxillary, completes for the palate bone its nasal 
foramen (fig. 26). 
Monotremata. — In the Ornithorhynchus the inferior margin of the vomer extends 
quite back to the posterior extremity of the hard palate, which is formed by the meeting 
of the pterygoids. In the Echidna it does not extend back so far. The condition of 
the intermaxillaries in the Ornithorhynchus is extremely interesting. The large bones 
which extend forwards from the maxillaries at a considerable distance from one another, 
and which give the form to the broad fiat bill, are beyond all question intermaxillaries, 
and correspond exactly to the intermaxillaries of the Bat, or any other animal in which 
the mesial-palatine processes of these bones are not developed. Utterly unconnected 
with these, in front of the vomer, and continuing on its upper aspect the vomerine 
groove, is the little bone which has been recognized both by Cuvier and Meckel as 
corresponding with the mesial-palatine processes of intermaxillaries, which it no doubt 
does ; but it is very interesting to find these represented by a bone so distinctly sepa- 
rated from the lateral plates of the intermaxillaries. It leads us to the consideration of 
the remarkable arrangement which exists in cases of cleft palate in the human subject, 
contrasted with the natural arrangement. 
In cases of complete cleft palate in the human subject the inferior margin of the 
vomer is free, and is seen in the middle line of the open roof of the mouth. The inter- 
maxillaiies, fused or separate, articulate with its anterior extremity, and continue for- 
wards in the same straight line, and support the incisor teeth when they are developed. 
They are entirely disconnected from the maxillaries, and are developed on the under 
aspect of the septal cartilage, which is a mesial structure ; while the maxillaries are 
developed in lateral laminae which, in these instances, fail to reach the middle line. 
Yet in the normal condition, marvellous as it may appear, the intermaxillary grows 
from the same centre of ossification as the maxillary and therefore must be con- 
* See on this subject, in the ‘ Comptes Eendus ’ (Dec. 1858 and Jan. 1859), various papers by M. Em. 
