LIASSIC CROCODILES. 135 



■and is rounded off at the summit. Tlie jDleurapophysis, or rib, is bifurcate at its 

 vertebral end, the tubercle being as long as tlie head and neck ; its distal end is 

 expanded into the liatcbet shape, the posterior angle being most produced, and 

 overlapping the pleurapophysis of the next vertebra behind. The same mechanism 

 for fixing and strengthening the neck thus existed for the advantage of the ancient 

 marine Crocodiles, as we find in those of the existing epoch. 



In the dorsal region the ribs exchange the hatchet for the ordinary lengthened 

 form, and soon begin to lose the head and neck, as in existing Crocodiles ; after 

 the fifth they no longer articulate with the centrum, only with the diapophysis, 

 which increases in antero-posterior extent and thickness, and presents an oblique 

 notch at its anterior angle, for the reception of the tubercle, now the only head of 

 the rib. The number of the dorsal ribs exceeds that of any existing Crocodilian, 

 being, as above indicated, 16 pairs. The spinous process is proportionally strong ; 

 in the "Whitby specimen it measures in most of the dorsal vertebra 2 inches in 

 antero-posterior extent, and 7 lines in transverse diameter or thickness ; the 

 height of these spines seems not to have much exceeded that of the cervical spines, 

 but they are more truncated at the summit. 



A posterior dorsal or lumbar vertebra of a Teleosaur from the Whitby lias, in 

 the collection of Mr. Eipley, corresponds with the vertebral characters of Teleo- 

 saurus in the slight concavity and circular contour of the terminal articular 

 surfaces of the body, and in the great antero-posterior extent of the spinous 

 processes ; but that of the diapophysis does not exceed one half the length of the 

 body of the vertebra, which is 2 inches 6 lines. This process is supported by two 

 short, obtuse, sHghtly developed ridges, which rise from the upper part of the side 

 of the body, as far apart as to include one third of the length of the body between 

 them, and converge to the under part of the process ; a similar ridge extends from 

 the upper part of the posterior end of the process obliquely backward to the base 

 of the postzygapophysis. The neural arch is anchylosed to the centrum in this 

 vertebra. The supporting buttresses of the diapophyses are not described by 

 Cuvier in the dorsal vertebras of the Caen Teleosaur ; nor have I met with any 

 dorsal or lumbar vertebi'se of the Whitby species, except the present, that was 

 sufficiently perfect to exhibit this character ; it may, however, be constant and 

 characteristic of the genus. It faintly indicates one of the most striking characters 

 of the vertebrge of Streptosiyondylm. The anterior and posterior margins of the 

 spinous processes are slightly excavated, and thus retain a character which is 

 transitory in the Crocodile, and peculiar to an early period of its existence. 



The bodies of all the vertebrsB are compressed laterally, and concave antero- 

 posteriorly at the sides ; but this character is more strongly marked in the anterior 

 caudal vertebrje, which are flattened along the inferior surface; these vertebrse 

 in the Whitby specimen were 2 inches 8 Lines in length. The diapophyses are 



