810 
DE. CLELAOT) ON THE EELATIONS 
orbits ; and the peculiarity of its position in the mammal consists merely in this, — that 
by the curving downwards of the frontal and vomerine neural arches, and the curving 
upwards of the frontal centrum, the latter is entirely concealed by the former. 
The Intermaxillariesin Beptilesand Osseous Fishes. — We now approach a most inter- 
esting series of intermaxillaries, which atford the clue to the explanation of the segment 
to which these bones belong. In the Crocodiles the arrangement of the intermaxil- 
laries is like that in the mammalia, but by the great elongation of the maxillaries they 
are far removed from the vomerine bones. The articulation of their anterior extremi- 
ties is like that in the Horse ; they pass up in front of the septal cartilage and close it 
in. In the Chelonians the nasals are absent ; and the intermaxillaries are united into a 
single bone, which is placed between the anterior extremities of the maxillaries, and in 
the Tortoise articulates with the vomer. From the Chelonians we pass to the Lizards, 
and in them also we find the intermaxillary single and articulating with the anterior 
extremities of the maxillaries ; but it differs from the chelonian intermaxillary by send- 
ing upwards and backwards in the middle line a process to articulate with the nasals, 
which corresponds to the processes projected upwards by the intermaxillary of the bird, 
and which is often the most developed part of the bone. In Varanus and others the 
nasals are represented by a single bone. 
In the Serpents we again meet with a single intermaxillary which articulates in the 
middle line with the nasals ; and as it is but loosely connected with the maxillaries, and 
forms the anterior extremity of the line of centra, it puts one strongly in mind of the 
arrangement in cases of cleft-palate in the human subject. 
It greatly resembles also another bone, viz. the nasal in fishes (nasal of Owen) ; and 
the resemblance consists in this, that, like the reptilian intermaxillary, the nasal of the 
fish, when present, forms the anterior member of the series of centra. 
Sometimes this relation of the nasal in fishes is very much disguised by the thicken- 
ing of the vomer which takes place in connexion with the development of vomerine 
teeth, — a thickening which gives to the vomer the appearance of projecting do'wn wards, 
and which often looks as if it formed the termination of the line of centra, while the 
extremity of the nasal appears to be situated altogether above that line. This is the 
case, for example, in the Cod ; but w'hen, in the fresh state, a vertical section is made 
through the nasal and vomer, it is seen that, not the vomer, but the extremity of the 
nasal bounds anteriorly the cartilaginous bar of the base of the skull (fig. 29). There 
is, in addition, a nodule of cartilage ^ attached in front of the nasal, in the Cod and 
many other fishes, which seems to be a portion of that bar, separated from the main 
part by the interruption of the nasal. But that the nasal lies in the line of centra is 
best seen in some of the fishes which have no vomerine teeth. It is beautifully seen in 
Malapterurus, in which the whole shape of the nasal singularly resembles the inter- 
maxillary of Boa or Python (fig. 30). 
One might well believe from its relation to the line of centra that the nasal of the fish 
* Eecognized as the vomer by Professor Goodsie, oj). cit. p. 140. 
