30 



ANATOMY OF VERTEBRATES. 



Ji^ 



nil, 



2 !5^ -J ct,X-«-* ^ 



C)QB|aBllin3D| 



The different elements of the pri- 

 mary segments are distinguished by- 

 peculiar markings : — 



The neurapophyses by diago- 

 nal lines, thus — 



The diapophyses by vertical 

 lines — 



The parapophyses by horizon- 

 tal lines — 



The centrum by decussating : 

 horizontal and vertical lines — ! 

 The pleurapophyses \>j diago- 

 nal lines — 



The appendages by dots — '..'.'.'. 

 The neviral spines and haemal sinnes 

 are left blank. 



In certain segments the elements 

 are also specified by the initials of 

 their names : — 



ns is the neural spine. 

 n is the neurapophj'sis. 

 j)l is the pleurapophysis. 

 c is the centrum. 

 h is the ha3mapophysis, also indi- 

 cated by the numbers 21, 29, 



44, 52, 58, 63, 64.' 



lis is the hasmal spine. 

 a is the appendage. 



The centrum is the most constant 

 vertebral element as to its existence, 

 but not as to its ossification. There 

 are some living fishes, and formerly 

 there were many, now extinct, in 

 which, whilst the peripheral elements 

 of the vertelira become ossified, the 

 central one remains unossificd ; and 

 here a few words are requisite as to 

 the developement of vcrtcbra\ 



§ 16. Di'vchpcmcnt of rerfebrcp. — 

 The central basis of the ncuroskcleton 

 is laid down in the embryo of every 

 vertebrate animal as a more or less 



' Sco 'Table or Synonyms, Spcciiil Homologies,' 

 indicated by numbers. 



for the names of tlic bones 



