A REPRESENTATIVE VERTEBRATE. FROG 



345 



Premaxilla 



Maxilla 



OJI 



Frontoparietal 



Occipital 



Squamosal 



Pterygoid 



Hyoid 

 Mandible 



Anterior 

 horn 



Hyoid 

 plate 



Posterior 

 horn 



Hyoid (ventral view) 

 Figure 228. Lateral view of skull and hyoid of bullfrog. 



Vertebral column 



The vertebral column (Fig. 226) or back- 

 bone consists of 9 vertebrae and a bladelike 

 posterior extension, the urostyle. Each verte- 

 bra consists of a basal centrum, which is 

 concave in front and convex behind, and a 

 neural arch through which the spinal cord 



passes. The neural arch possesses a short 

 neural spine, a transverse process on each 

 side (except on the first vertebra), and a pair 

 of articular processes called zygapophyses at 

 each end. The vertebrae are held together 

 by ligaments and move on one another by 

 means of the centra and zygapophyses. The 



Epistemum 



Suprascapufa 



y^ ^ Omosternum 

 -' — Scapula 

 Clavicle 



Glenoid fossa 



fpicorocoid 



Corocoid 



lum 



Acetabulum 



Mesosternum 



Xiphisternum 



Pubis- 

 Ischium 



Piectorot girdle and sternum (ventral viev/j 



Figure 229. Girdles of the frog. 



Pelvic girdle (side view) 



vertebral column thus serves as a firm axial 

 support which also allows bending of the 

 body. A frog has no ribs. 



* Although in this text the sternum is regarded 

 as a part of the axial skeleton, it is described with 

 the pectoral girdle because of the functional relation- 

 ship of the two structures. 



Appendicular skeleton 



The pectoral girdle and sternum * (Fig. 

 229) support the forclimbs, serve as attach- 

 ments for the muscles that move the fore- 

 limbs, and protect the organs lying within 

 the anterior portion of the trunk. They are 

 composed partly of bone and partly of 



