BY PROFESSOR J. T. WILSON. 725 



It was there suggested that this bone is morphologically an 

 anterior vomerine element. Its homology to at least a portion of 

 the palatine process of the premaxilla of other mammals was also 

 discussed, and was considered b}'- no means incompatible with 

 the vomerine theory propounded by the writer. 



In a paper subsequently published in these Proceedings (H), 

 Dr. R. Broom further discussed the homology of the palatine 

 process of the premaxilla in the mammalia generally. 



In this paper he summarised the arguments of the present writer 

 in favour of the essentially vomerine nature of the dumb-bell- 

 shaped bone, and held that "these arguments afford conclusive proof 

 that the dumb-bell-shaped bone belongs to the vomerine category 

 and is no part of the premaxilla," He further suggested the 

 term "prevomer" as preferable to that of "anterior vomer," 

 which the present writer, following the nomenclature of W. K. 

 Parker, had already applied to it. He then proceeded to advocate 

 the view, already contemplated by the writer, that the palatine 

 process of the premaxilla in other mammals "is itself a distinct 

 vomerine element, ankylosed or formed in connection with the 

 premaxilla." 



A further important view is, however, also put forward, viz., 

 that the so-called vomers of the Lacertilia, which are topographi- 

 cally related to the organ of Jacobson in these forms, are in 

 reality the homologues of the mammalian anterior or prevomers, 

 and not of the mammalian vomer. In support of this doctrine 

 he invokes the authority of W. K. Parker, who would seem to 

 have arrived at a similar conviction. 



These views of the nature of the dumb-bell-shaped bone elicited 

 a reply in 1896 from Professor Symington (12), who had previously 

 (13) upheld the theory that the dumb-bell-shaped bone represented 

 neither more nor less than the detached palatine processes of the 

 premaxilla. The paper was written before Dr. Broom's latest 

 contribution reached Europe, though this writer's views were 

 already to some extent known to Dr. Symington through a 

 previous paper by Dr. Broom dealing with the organ of Jacobson 

 in the Monotremata (i4). 



