164 



PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



LIGN. 35. FOSSIL VERTEBRA OF REPTILES ; TILGATE FOREST. 



(The figures are reduced in the proportions specified by the fractions.) 

 Fig. 1. Caudal vertebra of an unknown reptile. 



2. Chevron bone of IGUANODON: seen in front. 



3. Caudal vertebra of IGUANODON, viewed laterally in an oblique direction. 



3". Front view of the same. 



4. Caudal vertebra of IGUANODON, without either transverse process or 

 chevron-bone. The letter o marks the deep hollow left by the removal 

 of the transverse process, at the suture of the annular part. 



5. Vertebra of STREPTOSPONDYLUS? -^ na t. size. 



6. Lumbar vertebra of IGUANODON, with the spinous process broken off. 



7. Cervical vertebra of STREPTOSPONDYLUS? -^ na t. s i ze% 



c. The pair of posterior oblique processes. 



8. The bodies of two dorsal vertebrae of IGUANODON : viewed laterally. 

 The same letters refer to the analogous parts in the respective figures ; with 

 the exception of c, in fig. 7. 



a. The body, or centrum, of the vertebra: the letter denotes the anterior part. 



b. The annular part (neurapophysis), which surrounds the spinal cord, 

 c, c. The anterior articular or oblique processes. 



d. The spinous process of the annular part. 



e, e. The transverse processes, or parapophyses. 



f. The chevron-bone (hcemapophysis), or inferior spine of the vertebra. 



g. The single articulating head of the chevron-bone : the interspace seen 



in the front view, fig. 2, is for the passage of the large blood-vessels 

 which supply the tail. 

 h. The spine of the chevron-bone. 



i. The shaded spot, d, denotes the medullary cavity of the annular part. 

 o, o. Mark the sutures which connect the annular part with the body of the 



vertebra. 



w, w. Indicate the place of attachment of the chevron-bone, which in the 

 Iguanodon is always single. 



