00 2 mammalian and reptilian vomerine bones, 



The Lacertilian "Yomer." 



The bones in the lizard which have usually been regarded as 

 vomers agree with the mammalian vomer in lying for the most 

 part in the anterior half of the skull, and in articulating with the 

 premaxillaries and the palatines. But here the resemblance 

 ceases; and when we compare the intimate relations of the bones 

 we tind it impossible to regard them as homologous. The 

 mammalian vomer is a median element developed in connection 

 with that part of the basicranial axis which is formed by the 

 united trabeculse; the lacertilian " vomer " is a paired element 

 which is formed in connection with the nasal capsules. 



Though many figures of sections of the nasal capsules of lizards 

 and snakes have been published by Born, Parker, Seydel, and 

 others, perhaps the best illustration is a figure by Seydel (12) of 

 a reconstructed model of the nasal capsule of Lacerta, in his 

 paper on the organ of Jacobson of Chelonia. From this figure, 

 which I have reproduced, it will be seen that the nasal capsule 

 consists of an irregular cartilaginous sac with three openings, one 

 for the anterior and one for the posterior nasal opening, and a 

 third opening towards the brain to admit the nasal nerves. The 

 external wall is much folded, and the inner wall is to some extent 

 formed by the nasal septum. How much of the septum belongs 

 to the nasal capsule, and how much is trabecular, is difficult to 

 decide. By the side of the base of the septum is a long narrow 

 cartilaginous band which is united to the nasal floor proper in 

 front, and to the posterior wall of the capsule behind, and which 

 forms to some extent the lower and inner wall of the capsule. 

 This is the paraseptal cartilage. If this lacertilian capsule be 

 compared with the nasal capsule of the marsupial it will be seen 

 that the two are essentially similar in structure — the marsupial 

 capsule only differing in being somewhat simpler. In the 

 marsupial — at least in the fcetal condition — the paraseptal 

 cartilage stretches from the nasal floor in front to the hinder part 

 of the nasal capsule exactly as in the lizard. B}^ Parker the 

 paraseptal cartilage was regarded as a development of the 



