THE SKELETON OF THE VERTEBRATE HEAD. 119 



find a complete although cartilaginous vomer. Of that part 

 of the extended nasal septum of the crocodiles, corresponding 

 to the mammalian nasal septum, the only ossified portion is 

 an elongated single or double slip along the lower edge of its 

 ethmoidal region, and continuous with the elongated pre- 

 sphenoidal centrum. Professor Owen considers this slip of 

 bone as the vomer. I will only observe at present that, hold- 

 ing the vomer to be invariably in relation to the intermaxil- 

 laries, I can only conceive, as the vomer in the crocodile, that 

 elongated cartilaginous portion of the nasal septum which 

 extends beneath the elongated nasal bones to the intermaxil- 

 lary suture. 



Vomerine Sclerotome in Typical Lacertians. In the proper 

 lizards this sclerotome is imperforate. The intermaxillaries 

 not only close in at the palate, but in front also ; the more or 

 less elongated and combined ascending processes joining the 

 united or distinct nasal bones. The centrum is represented 

 by the anterior part of the cartilaginous septum. The two 

 bones, usually described as the double vomer of the lizard, 

 belong, as I shall endeavour to show in the sequel, to the suc- 

 ceeding sclerotome the ethmoidal. 



Vomerine Sclerotome in Birds. The yomerine sclerotome 

 of the bird consists principally of the intermaxillaries, but 

 partly of the persistent anterior portion of the primordial 

 cranium. The intermaxillaries speedily unite below and in 

 front, so as to form the first and principal part of the 

 beak. Their united ascending processes extend up to the 

 so-called " principal frontal bone," and separate completely 

 the so-called nasal bones. In the sequel the evidence will be 

 adduced on which I found my belief that the bone called in 

 birds the "frontal," or "principal frontal," is not the frontal 

 of the mammal ; but that the two so-called nasal bones in the 

 bird are the two halves of that bone which in the mammals 

 is called frontal. If so, where are the nasal bones of the bird ? 



