374 



CROCODILIA. 



processes arising from the neural arch. In the sacral vertebrae the 

 ribs are attached to the centrum and neural arch. The anterior cau- 

 dal vertebrae bear ribs ankylosed to the centrum and nem-al arch. 

 Chevron bones are present, attached to the posterior part of the centra 

 of the caudal vertebrae, except on the first and the posterior vertebrae. 



The sternum consists anteriorly of a rhomboidal plate of 



cartilage to the sides of which are 

 articulated the sternal portions of 

 two thoracic ribs, and of a narrower 

 posterior portion, also cartilaginous, 

 which soon bifurcates and has at- 

 tached to it from five to seven pairs 

 of sternal ribs. A slender inter- 

 clavicle lies on the ventral surface 

 of the rhomboidal part of the ster- 

 num. 



The thoracic ribs (Fig. 202) con- 

 sist of a vertebral portion of which 

 the distal part is feebly ossified, and 

 of a sternal portion also feebly ossi- 

 fied and joining the sternum. The 

 former in the case of several of the 

 anterior ribs carry on the hinder 

 side of their dorsal more ossified 

 portion an uncinate process in the 

 form of a small cartilaginous (some- 

 times partly ossified) plate. 



The so-called " abdominal n'6s " 

 FIG. 203.— Ventral view vt "tkiiU of (Fig. 202, Sta) are membrane bones 



Belndon kapffi to sliuw the para- , , , , , , p » 



-■ • placed on the ventral surface of 

 the rectus abdominis muscles. 

 They are usually seven in number 

 and consist on each side of 

 two curved rods ; they are not joined in the middle line. 

 In the skull the dorsal and lateral bones are roughly pitted. 

 There is a low cartilaginous interorbital septum with, a mem- 

 branous interspace, and the presphenoid and orbitosphenoid 

 region remains cartilaginous. There is an alisphenoid, and a 

 separate prootic, but the epiotic fuses with the supraoccipital 

 and the opisthotic with the exoccipital. The occipital condyle 



suchal choanae (after Zittel). 

 Bo basioccipital ; Ch choanae ; 

 Exo exoccipital ; Jti jugal ; Mx 

 maxilla ; PI palatine ; Pmx pre- 

 maxilla ; Pt pterygoid; Qu quad- 

 rate ; Vo vomers. 



