450 ME. ST. GEOEaE MTVAET ON THE 



Looking mainly dorsad in the cervical region, they come to look mainly inwards in 

 the dorsal region. 



Postzygapophyses. 



These may exist without prezygapophyses, as in the atlas. 



They undergo changes of form and direction corresponding with those of the prezy- 

 gapophyses, but they never become quite so small as do the latter in the dorsal region. 



Metapophyses. 



These processes would escape notice were it not for their recognition through their 

 more developed homologues in other animals. 



They are more or less to be distinguished outside and ventrad of the prezygapophyses 

 from the fourth vertebra to about the eighteenth, after which they seem to merge in 

 the wider diapophysial expansion. 



Hyperapophyses. 

 These are only conspicuous in the axis and the third and fourth cervical vertebrae, where 

 they are situated above the postzygapophyses. Rudiments of them are to be found on 

 the atlas, and on vertebrae postaxial to the fourth, till perhaps the tenth vertebra. 



Paraxial Parts. 



By paraxial parts ' I mean those portions of the skeleton which diverge from the 

 centra and nem-al arches laterally, and tend to surround the visceral cavity. 



They include: — 1, upper transverse processes or diapophyses; 2, lower transverse 

 processes or parapophyses ; 3, pleurapophysial parts, i. e. the ribs, with their capitular 

 and tubercular portions, sternal ribs, and sternum, or parts representing the whole or 

 portions of each pair of capitula and tubercula, with only a rudiment, or without any 

 rudiment, of more distal pleurapophysial elements. 



These parts considered as one whole are, of course, as to size, most developed and 

 most differentiated in the true dorsal vertebrae. 



They are least differentiated in the true caudal region, where they stand out laterally 

 as simple imperforate " transverse processes." 



Diapophyses. 

 These are, with the neural spines, the most constant of all the processes, appearing 

 even in the lumbar, dorsal, and caudal regions, where there are no zygapophyses. 



More or less antero-posteriorly extended in the cervical region, they are much so in 

 the dorsal one. In the lumbar region they are long and slender, singularly remote 

 from their respective parapophyses, and widely diverging from the latter. 



In the first four postsacral vertebrae the diapophyses quite coincide with the para- 

 ' See p. Z. S. 1S70, p. 260, note ; and see also Trans, of Linnean Society for April 21, 1870. 



