54 The Alligator and Its Allies 
thin and triangular in shape, resembling in contour 
a large, mammalian epiglottis. It forms an arch 
over the space between the skull and the front 
of the atlas proper. Reynolds calls it the pro- 
atlas. 
The Axis. The centrum differs from those fol- 
lowing it (described above) mainly in its close 
articulation (not fusion) with the large odontoid 
process; this process not only projects into the 
atlas, as is usually the case, but articulates with its 
postero-lateral border on each side, and is dis- 
tinctly visible in a lateral view of the neck (Fig. 17, 
3). Like the rest of the cervical vertebre the poste- 
rior surface of the centrum is convex. The neural 
arch of the atlas differs from those following 
mainly in having a much wider (in an antero-pos- 
terior direction) neural spine. The lateral pro- 
cesses and those bearing the prezygapophyses are 
also less strongly developed than on the following 
vertebre. 
The Thoracic Vertebre. ‘The first thoracic verte- 
bra differs scarcely at all from the ninth cervical; 
and the tenth thoracic differs from the first lumbar 
only in bearing a short rib. Only the first three 
thoracic centra bear the hypapophyses noted in 
connection with the cervical vertebre. The ribs 
of the first two thoracic vertebre articulate with 
them by two processes, as in the typical cervical 
vertebre; the other ribs articulate only with the 
transverse process. The fourth thoracic may be 
