SKELETON OF THE CROCODILE. THE HYOID. 259 



which in young skulls rather readily becomes detached. The 

 remaining mandibular bone is the coronoid (fig. 45, 23), a very 

 small bone of irregular shape attached to the angular below, 

 and to the supra-angular and splenial above. 



(c) THE HYOID. 



The hyoid of the Crocodile consists of a wide flattened 

 plate of cartilage, the basilingual plate or body of the 

 hyoid, and a pair of cornua. 



The basilingual plate (fig. 53, 1) is rounded anteriorly 

 and marked by a deep notch posteriorly. The cornua (fig. 

 53, 3), which are attached at a pair of notches near the middle 

 of the outer border of the basilingual plate, are partly ossified, 

 but their expanded ends are formed of cartilage. They pass 

 at first backwards and then upwards and inwards. They 

 are homologous with part of the first branchial arches of 

 Selachians. 



The columella and extra-columella have been already de- 

 scribed (p. 251). 



C. THE RIBS AND STERNUM. 



Thoracic ribs. 



The Crocodile has ten pairs of thoracic ribs, all except 

 the last one or two of which consist of three parts, a verte- 

 bral rib, an intermediate rib and a sternal rib. 



Of the vertebral ribs the third may be taken as a type, 

 it consists of a curved bony rod which articulates proximal!} 7 

 with the transverse process of the vertebra by two facets. 

 The terminal one of these, the capitulum or head, articulates 

 with a notch on the side of the transverse process; the other, 

 the tuberculum, which lies on the dorsal surface a short 

 distance behind the head, articulates with the end of the trans- 

 verse process. From near the distal end an imperfectly ossified 

 uncinate process (see p. 190) projects backwards. 



The intermediate ribs are short and imperfectly ossified ; 

 they are united with the sternal ribs (fig. 46, 3), which are large, 



172 



