ANATOMY OF VERTEBRATES. 



67 



between it and the ha?mapophysis. A small cartilaginous appen- 

 dage is attached to some of the ribs. 



The lumbar vertebras are those in which the diapophyses cease 

 to support moveable pleurapophyses, although they are elongated 

 by the coalesced rudiments of such, ib. e, f, g, h, which are distinct 

 in the young Crocodile. The length and persistent individuality 

 of more or fewer of these rudimental ribs determines the number 

 of the dorsal and lumbar vertebra? respectively, and exemplifies 

 the purely artificial character of the distinction. The number of 

 vertebra? between the skull and the sacrum is twenty-four. In 

 the skeleton of a Gavial, I have seen thirteen dorsal and two 

 lumbar; in that of a Crocodihis cataphractus twelve dorsal and 

 three lumbar ; in those of a Crocodilus acutus and Alligator lucius, 

 eleven dorsal and four lumbar, fig. 57, which is the most com- 



mon number. C 



uvier assions 



five lumbar vertebra) to Croc. 



55 



Diagram of posterior trunk-vertebra, Crocodile, cc. 



biporcatus. But these varieties in the developement or coales- 

 cence of the stunted pleurapophysis are of no essential moment. 

 The coalescence of the rib with the diapophysis obliterates of 

 course the character of the 'costal articular surface,' which we 

 have seen to be common to both dorsal and cervical vertebra?. 

 The lumbar zygapophyses have their articular surfaces almost 

 horizontal, and the diapophyses, if not longer, have their antero- 

 posterior extent somewhat increased ; they are much depressed, 

 or flattened horizontally. 



The sacral vertebra?, fig. 57, S, are very distinctly marked by 

 the flatness of the coadapted ends of their centrums ; there are 

 never more than two such vertebra? in the Crocodilia, recent or 

 extinct : in the first the anterior surface of the centrum is concave, 

 in the second the posterior surface ; the zygapophyses are not 

 obliterated in either of these sacral vertebra?, so that the aspects of 



F 2 



