The Relationship of the Fremaxilla in Bears. 



By 



R. J. Anderson, 



Galway. 



(With pi. IX and 5 figs, in the text.) 



The premaxilla has excited so much interest that some remarks 

 on its conditions and relationships in the Bears and their allies maj not 

 be without value. Meckel remarked. „Das Zwischenkieferbein bietet 

 fast noch grössere Verschiedenheiten dar als das eig-entliche Ober- 

 kieferbein. He considers the bone as composite so far as it consists of 

 a facial limb, and a horozontal palatine limb. These are so very di- 

 stinct parts in many mammals that one is apt to jump at the con- 

 clusion that a separate centre of ossification may lurk somewhere for 

 the palatine part. The dumb - bell - shaped bone in Ornithorhychus 

 seems to bridge over the difficulty, but Meckel was of opinion that he 

 had found a homologue to it in the two -toed sloth. Owen thought 

 that the Prenasal of the pig was its homologue. Turner took ex- 

 ception to the latter statement, and the Consensus of opinion since 

 Rudolphi, Blainville and Meckel, seems to be that the Central plate is 

 to be regarded as Premaxillary. The fact that the bone is unpaired 

 and that it bears certain relations reminding one of the condition in 

 certain reptiles suggests vomerine affinities. 



The Premaxilla has also excited some interest because of the part 

 it has played in the vertebrate theory of the skull. It is now no longer 

 even mentioned that the skull consists of vertebral segments, but seg- 

 mentation of the head is at an early period freely admitted for the 

 vertebrates. 



