BY R. BROOM. 547 



He showed that in this Crocodilian the vomer has its anterior end 

 greatly developed, and that in connection with this anterior 

 development there is a cartilaginous sac, which he concluded was 

 most probably the cartilaginous capsule of Jacobson's organ. He 

 discusses at some length the question of the homology of the 

 bony supports of Jacobson's organ in mammals and lizards; and 

 concludes that what he calls the prepalatine lobe of the vomer in 

 the Caiman is homologous with the "anterior paired vomer" of 

 Parker in mammals. These paired vomers he regards as morpho- 

 logicalty portions of the vomer proper which have become separated 

 by absorption. According to this view the lacertilian " vomer " 

 would be morphologically equivalent to the mammalian vomer 

 and anterior vomers combined. 



In 1894 Wilson (6), of Sydney, published a paper giving a very 

 full description of the dumbbell-shaped bone of OrnitJiorhynchiis, 

 and discussing at some length the homologies of the bone. He 

 was specially impressed by the fact of its relationship to the 

 vomer being apparently much more important than its relation- 

 ship to the premaxillaries; and was led to conclude that the 

 dumbbell bone is no part of the premaxillary, but a true anterior 

 vomer homologous with the small anterior vomers discovered by 

 Parker in the early stages of a number of long-nosed mammals. He 

 seems inclined to the opinion, though he does not explicitly state 

 it, that the dumbbell bone is also the homologue of the lacertilian 

 so-called "vomer." 



In the following year, having been for some time engaged in 

 the study of the comparative anatomy of Jacobson's organ, and 

 having come across one or two new facts bearing on the subject, 

 I (7) published a short paper on the homology of the palatine 

 process of the mammalian premaxillary. In the Marsupials which 

 I had studied, I had found the palatine process to be invariably 

 developed along with the premaxillary, and with no trace of a 

 distinct anterior vomer; but as the palatine process invariably 

 formed a splint to the cartilage of Jacobson, similar to that 

 formed by the dumbbell bone in Ornithorhynchus, and having 

 relations very similar to those of the so-called "vomer" in 



