TIIK SKKLETON OK TIIK VKUTEHKATK IIKAD. 105 



called " vomer," and as those of the lizard, seq)ent, and frog to 

 the bones hithei-to called " palatal " in tliese three forms. I 

 therefore apply provisi<jnally the term ento-pterygoid to the 

 so-called " ^■omor " of the bird, to the posterior ])ai"t of the so- 

 called " vomer " of the clielonian, to the corresponding bony 

 piece in tlie crocodiles, to the so-called "palatals" of tlie 

 ophidian, lacertian, and batrachian, to the "bones of Bertiu," 

 and their representatives in the mammal. 



Tlic Cunstitution of tJic Nasal Fossa, and tlic Relative Posi- 

 tions of the External and Internal Karcs. — Tlie details necessaiy 

 for the morphological examination of the rhinal, vomerine, 

 ethmoidal, and pre-sphenoidal sclerotomes, have involved a 

 number of facts connected with the varied constitution of the 

 nasal fossie in the different vertebrate fonns. As, liowever, 

 the constitution of these fossae has important bearings on the 

 morphology of the entire cranium, I shall briefly direct atten- 

 tion to the subject. 



The only perfect form of nasal fossas is that presented by 

 the mammal. They consist of the entire neuro-htemal cavities 

 of the rhinal and vomerine, combined with the ha?mal ca^^ties 

 of the ethmoidal and pre-sphenoidal sclerotomes. That portion 

 of the combined nasal fossa? which consists of the cavities of 

 the rhinal and vomerine sclerotomes, is divided in the mesial 

 plane by the centrums of those sclerotomes ; while the 

 dependent portion of the ethmoidal centrum, and the posterior 

 portion of the vomerine centrum, divide in the same manner 

 that part of the combined fossrc which consists of the luemal 

 cavities of the ethmoidal and pre-sphenoidal sclerotomes. The 

 manmialian nasal fossfu are therefore bounded in front by the 

 walls of the neuro-hiemal chambers of two catacentric scleit)- 

 tomcs ; and posteriorly by the cataccntrically divided h;vmal 

 chambers of a demicataccntric and diacentric sclerotome. 



As the hanual portions of the cephalic somatomes are 

 separated frnm nn(> mu.tlicr in their early embryo eondition by 



