ANATOMY OF VERTEBKATES. 69 



as it approaches its fellow to complete the second pelvic haemal 

 arch. The size of these elements of the hsemal arch, and their 

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

 names : their diverging appendage being developed into a potent 

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

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

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

 physes extend from h 1,2, 3, to /* 6, 5, 4 : the haemal spines, mostly 

 confluent, are co-extensive from hs to io, where they expand as a 

 cartilage between 6 and 5. The pair of haunapophyses, h 1, are 

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

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

 is called ' episternum,' 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 CrocodiUa, ib. 10, and partly bony in old 

 specimens. The abdominal haemapophyses, represented by the 

 ' intersectiones tendineae musculi recti abdominis' of anthropotomy, 

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



The pleurapophysis is reduced to a transverse process in the 

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

 has no articular surface for the haemapophyses : 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 caudal vertebra the transverse processes disappear, 

 the centrum becomes compressed, and the neural and hsemal 

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

 tory tail, to near its pointed termination. 



The characters of the trunk-vertebrae of existing CrocodiUa, 

 especially their procoelian type, are those which their predecessors 

 presented throughout all the tertiary series of deposits, 1 and by 

 some species from cretaceous beds. 2 But in all the secondary 

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

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

 present, it shows reverse positions to the procoelian type, e. g. in 

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

 thence termed ' Streptospondylus.'' A similar ( opisthoccelian ' 

 modification is presented by the cervical and anterior dorsal 

 vertebrae of the more gigantic Cctiosaurus ; and, in a minor degree, 



1 clxiii., part iii. p, 117, pis. 1 d, 3, 3 a. 

 z Crocodilus basifissus, clxiv. p. 3S0. 



