ANATOMY OF VERTEBRATES. 69 



as it approaches its fellow to complete the second pelvic lifcmal 

 ai'cli. The size of these eleinents of the ha;mal arch, and their 

 distinctive shapes, have obtained for them, in anthropotomy, special 

 names : their divergino- appendage being developed into a potent 

 locomotive member. The crocodile yields a clear view of the serial 

 homologies of the hremal elements along the trunk. In fig. .56, 

 they are sketched as seen from the dorsal aspect. The hmmapo- 

 physcs extend from h i, 2, 3, to h 6, 5, 4 : the lu^mal spines, mostly 

 contlucnt, are co-extensive from lis to 10, where they expand as a 

 cartilage between c, and 5. The pair of ha^mapophyses, /( 1, are 

 called 'coracoids,' and bear the special number 52: the pair, 5, are 

 the ' pubic bones ' ; the pair, 4, the ' ischia.' The hremal spine, hs, 

 is called ' ej)isterni"im,' the succeeding more or less confluent spines, 

 9, form the ' sternum ' : in Man their abdominal continuation, not 

 quitting the fibrous tissue-state, is called ' linea alba ' ; it be- 

 comes cartilage in the Crocodilia, ib. 10, and partly bony in old 

 specimens. The abdominal hsemapophyses, represented by the 

 'iutcrsectiones tendineaj musciili recti abdominis' of anthrop<.>tomy, 

 are commonly ossified, each from two centres, in old Crocodilia. 



The i^leurapophysis is reduced to a transverse process in the 

 first caudal vertebra, fig. 55, I; which, besides being biconvex, 

 has no articular surface for the ha;mapophyses : these elements 

 reappear in the succeeding segments, detached, as in the lumbar 

 series, from their pleurapophyses, but articulated to the centrum 

 directly, fig. 7, with a backward displacement, to the interspace 

 between their own and the succeeding vertebra, fig. 57, h. After 

 the fourteenth caridal vertebra the transverse processes disappear, 

 the centrum becomes compressed, and the neural and haemal 

 spines give adequate vertical extent to the long and strong nata- 

 tory tail, to near its pointed termination. 



The characters of the trunk-vertebrai of existing Crocodilia, 

 especially their prococlian type, are those which their predecessors 

 presented throughout all the tertiary series of deposits,^ and by 

 some species from cretaceous beds.'^ But in all the secondary 

 series below the chalk, the Crocodilia present flattened or sub-con- 

 cave vertebral surfaces ; or, if the cup-and-ball structure be 

 jiresent, it shows reverse positions to the proccelian type, e. g. in 

 the anterior trunk-vertebra3 of the genus of oolitic Crocodilian, 

 thence termed ' Streptosporuhjlus.^ A similar ' opisthocoelian ' 

 modiflcation is presented by the cervical and anterior dorsal 

 vertebra; of the more gigantic Cetiosaurus ; and, in a minor degree, 



' CLXiii., part iii. p. 117, pis. 1 D, 3, .3 a. 

 - Crocodilus basijissus, CLXIV. p. 380. 



