THE SKELETON OF THE TURTLE. THE HYOID. 231 



The articular (fig. 38, 1 1) is expanded, and with the supra- 

 angular forms the concave articulating surface for the quadrate. 



The splenial (fig. 38, 10) is a thin plate applied to the inner 

 surface of the posterior part of the mandible. 



The angular (fig. 38, 13) is a slender plate of bone lying 

 below the supra-angular and splenial. 



(3) THE HYOID. 



The hyoid apparatus is well developed, parts of the first two 

 branchial arches being found, as well as of the hyoid proper. 

 It consists of a more or less oblong flattened basilingual 

 plate or body of the hyoid which represents the fused 

 ventral ends of the hyoid and branchial arches of the embryo, 

 and is drawn out into a point anteriorly. The greater part is 

 formed of unossified cartilage, but at the posterior end it is 

 bilobed, and a pair of ossified tracts occur. To its sides are 

 attached three pairs of structures, which are portions of the 

 hyoid and first and second branchial arches respectively. 



The free part of the hyoid consists of a small piece of 

 cartilage attached to the anterior part of the basilingual plate 

 at its widest portion (fig. 53, 2). 



The anterior cornu or free part of the first branchial 

 arch is much the largest of the three structures. Its proximal 

 portion adjoining the basilingual plate is cartilaginous, as is 

 its distal end ; the main part is however ossified. 



The posterior cornu or free part of the second branchial 

 arch (fig. 53, 4) consists of a short flattened cartilaginous bar 

 arising from the bilobed posterior end of the basilingual plate. 



The hyoid apparatus has no skeletal connection with the 

 rest of the skull. 



2. THE APPENDICULAR SKELETON. 



This includes the skeleton of the two pairs of limbs and 

 their girdles. 



THE PECTORAL GIRDLE. 



The pectoral girdle has an anomalous position, being 



