32 PROCEEDINGS OF THE ACADEMY OF [1894. 



HOMOLOGIES OF THE ALISPHENOID AND PETROMASTOID BONES IN 



VERTEBRATES. 



BY HENKY C. CHAPMAN, M. D. 



To those unfamiliar with modern views upon the morplioloiify of 

 the skull it may not be known that any difference of opinion still pre- 

 vails among anatomists as to what bones in the skull of the lower ver- 

 tebrates should be regarded as homologues or representatives of the 

 great wing of the sphenoid and petromastoid in the skull of Man and 

 other mammalia. Considering the numerous and important paheon- 

 tological and embryological researches made in recent years, and in 

 view of the fact that the remains of extinct animals and the develop- 

 ment and structure of existing ones have been described so elabor- 

 ately, it might naturally be supposed that the question of the special 

 homologies of the bones of the skull would have long since been de- 

 finitely settled. 



So far, however, from this being the case, as a matter of fact anato- 

 mists, in certain instances at least, on the one hand designate the 

 same bone by different names and on the other, different bones 

 by the same name. The confusion of ideas thus engendered by ob- 

 scure nomenclature makes it often very difficult to understand what 

 particular bone is referred to, especially when the description relates 

 to the cranial bones of some extinct animal. Apart from this con- 

 sideration it is obvious that unless the special homologies of the bones 

 of the skull of different vertebrates are determined, and identical 

 bones be designated by the same name, it will be impossible to assign 

 to an animal its proper position in the order of Nature or determine 

 its phylogeny in the light of evolution, especially if the animal be 

 au extinct one and its natux-al affinities obscure. The hope of dis- 

 sipating some of the confusion prevailing as to the nomenclature of 

 certain of the bones in the skull of Man and other vertebrates prompts 

 the author to submit a resume of some well-known osteological fsicts 

 with, however, an interpretation of the same not hitherto presented, at 

 least as far as known to him. Even if the latter be not accepted, 

 the determination of the synonyms of the bones in question may, at 

 least, not prove superfluous hereafter to co-workers in this field 

 of research. 



