Sixth Day, 



Skeletal System (continued). 



C. The Skull. 



1. Remove the skin and other tissues from the top of the skull and observe 

 the large fronto-parietals, nasals, supra-ethmoid, premaxillse, maxillae, 

 squamosals, exoccipitals, and pro-otics. The quadrato-jugals are very 

 inconspicuous. The extrastapedial plate of cartilage is well marked and 

 the bony columella may be seen lying underneath it. The sides of the skull 

 are ossified and may represent the orbitosphenoids and alisphenoids of higher 

 types. The supra-occipital consists of a piece of cartilage. 



Supra-ethmoid 



Squamos 



Occipital condyle- ; I 



Fo-amen magivj 



FiG. 15. — Dorsal view of Skull of Xenopus and Rana. 



[In the Frog there is no supra- ethmoid present, but a sphenethmoid closes 

 the front of the cranial cavity. The sides of the skull are cartilaginous. A 

 quadrato-jugal is well marked, but the quadrate consists of a piece of cartilage 

 at the posterior end of the quadrato-jugal between the pterygoid and the squamosal. 

 The lower jaw articulates with it. The columella is usually not well shown.'] 



Make a drawing of the dorsal side of the skull. 



36 



