12G ON THE VERTEBRATE SKULL. 



sphenoid and with the vomer ; while the outer, or orbital, 

 processes articulate with the so-called lateral masses of the 

 ethmoid and with the maxilla; so that the upper part of each 

 palatine bone is directed, from the cranio-facial axis, with which 

 its inner end is connected, outwards and forwards (Fig. 54). The 

 third pair of bones, the Pterygoids, are the internal pterygoid 

 processes, — bones which are originally quite distinct from the 

 sphenoid, while the external pterygoid processes are of a very 

 different character, being mere outgrowths of the alisphenoids. 

 These are connected with the basi-sphenoid (or rather with the 

 lingulce sjihenoidales) , above, and, in front, with the palatines, 

 while their planes are directed backwards and somewhat out- 

 wards. The fourth pair of pre-oral bones — the Maxillee — are 

 connected in front and internally with the premaxillae, and 

 behind and internally with the palatines, but they nowhere come 

 into direct contact with the cranio-facial axis, at least primarily. 

 I make the latter qualification because the vomer articulates 

 with the superior surface of the palatine plates of the rnaxillae, 

 and it may be said that, in this way, the maxillae do unite with 

 the cranio-facial axis. This articulation, however, has nothing 

 to do with the primitive connections of the bones, but depends 

 upon a modification of the maxillae peculiar to the higher 

 vertebrata. The bony apertures — called " posterior nares " — in 

 Man, for example, are structures of a totally different character 

 from, and superadded to, what are called the posterior nares 

 in a frog, or ordinary lizard, or bird. In these lower Verte- 

 brates, the posterior nares are apertures, bounded on the inner 

 side, by the vomer ; on the outer side and behind, by the 

 palatine bones; in front, by the premaxillae and maxillae. In 

 Man, on the other hand, the apertures so called are limited, it is 

 true, on the inner side by the vomer, and on the outer side 

 by the palatine bones ; but they are also bounded below and in 

 front by the palatine bones, and the premaxillae and maxillae 

 have nothing to do with them. On looking closely into the 

 matter, however, it will be found that that region of the palatine 

 which forms the outer and inferior boundary of the posterior 

 nares of Man is a something which has no representative in the 

 lower Vertebrate. 



