THE SKELETON OF THE VERTEBRATE HEAD. 127 



retain their connection with the neural portion of their own 

 sclerotome, being attached superiorly to the lateral masses of 

 the ethmoid, and to the frontal. They are not articulated, as 

 in the fish, to their centrum ; but those connections to the 

 neurapophyses and metaneurapophyses, which in fish are 

 affected by ligaments, are sutures in the mammal. In the 

 sequel it will be shown, that of the two connections of the 

 maxillary that to the frontal, and that to the lateral ethmoid 

 the former is the most constant ; presenting in my opinion 

 the fundamental discriminative character of the remarkably 

 modified frontal of the bird, reptile, and amphibian. 



The Ethmoidal Sclerotome in the Bird. The ethmoidal 

 sclerotome is remarkably modified in the bird. It forms no 

 part of the cranium proper, but assumes the position and 

 structure of a facial sclerotome. The bird, like the mammal, 

 has two proper facial sclerotomes. In the former there are 

 the vomerine and the ethmoidal ; in the latter the rhinal and 

 vomerine. In the majority of birds, also, the ethmoidal 

 sclerotome, along with the vomerine, moves more or less freely 

 on the presphenoidal. It is, moreover, peculiar in being 

 chiefly devoted to the economy of the organs of smell ; in 

 having its metaneurapophyseal elements separated from one 

 another by the passage backwards of the conjoined ascending 

 processes of the intermaxillaries ; in the feeble development 

 of its hasmapophyses ; and in its cavities being altogether 

 neural, its neurapophyseal elements forming more or less of 

 its palatal aspect. 



The metaneurapophyses of the ethmoidal sclerotome of 

 the bird are the so-called nasal bones. From their invariable 

 connections with the maxillaries, I cannot see in these " nasal 

 bones " aught else than the proper frontal bones the frontals 

 of the mammal. They are separated from one another by the 

 ascending processes of the intermaxillaries ; a circumstance 

 which does not militate against their being the right and left 



