286 



this palatine process normally develops independently of the pre- 

 maxillary bone, and that, in certain animals, it remains independent 

 through life. That the vomer of the lizard and snake is the homo- 

 logue of the vomer of the Ichthyopsida Broom does not feel warranted 

 to assert, but he attributes to Sutton the statement, "that the pa- 

 latine process of mammals is the homologue of the 'vomer' of the 

 Ichthyopsida". What Sutton says is (No. 43): "Careful consideration 

 of the two skulls convinces me that the prepalatine centres of the 

 mammalian maxillae represent the piscine vomerine bones". And the 

 prepalatine center here referred to by Sutton is defined as one that 

 "forms the palate process of the maxilla and a considerable portion 

 of the inner wall". It is accordingly the palatine process of the maxil- 

 lary bone, and not that of the premaxillary, that Sutton identified 

 as the homologue of the piscine vomer, a wholly different and erro- 

 neous conclusion, it seems to me. 



Summary. 



In fishes, the Cyclostomata being here left wholly out of con- 

 sideration, there are, according to generally accepted views, two rows 

 or arches of teeth, one or both of which may appear in the upper 

 jaw. These two rows or arches of teeth are defined as a pterygo- 

 palato - vomerine arch, and a premaxillo - maxillary one. In Elasmo- 

 branchs, according to Rose (No. 34), the pterygopalato-vomerine arch, 

 alone, is found. In the chondrosteous Ganoids it is probably also this 

 arch alone that is found. In the Dipnoi it is also this arch alone; 

 or this arch with the possible addition of the premaxillary part of the 

 other arch, according as certain of the teeth of these fishes are con- 

 sidered as vomerine or premaxillary ones. In the Teleostei either 

 both arches may be found, or the premaxillo - maxillary arch alone; 

 but the maxillary part of the premaxillo-maxillary arch is much more 

 frequently untoothed than toothed (Sagemehl), the pterygopalatine 

 teeth frequently replacing, functionally, the maxillary ones. The maxil- 

 lary teeth, when found, are planted in a bone that is usually (always?) 

 moveably connected with the other bones of the skull, and hence does 

 not ofi'er the solid resistance to the mandibular teeth that the pterygo- 

 palatine ones do. 



The pterygopalatine teeth thus play a much more important 

 role in fishes than the maxillary ones, and these maxillary teeth do 

 not appear in the line of fishes until the Teleostean-like Ganoid, Amia, 

 is reached, unless it be assumed that they are found in Acipenser, 

 Lepidosteus, and Polypterus. This assumption, to say the least, seems 



