214 THE BIOLOGY OF THE ANIliIAL 



two pre-maxillae. What is their shape ? Note 

 the ascending process which each bears. "What 

 is the direction of the process? How are the 

 pre-maxillary bones united to each other ? To 

 the nasal bones ? Extending backward from the 

 lower end of each pre-maxilla find the maxil- 

 lary bone. How far back can you trace it? 

 What is its shape ? What is the shape of the 

 lower edge ? Note the teeth. On what part of 

 the maxilla are they borne ? How are they ar- 

 ranged ? What is their shape ? Do they vary in 

 shape and size? How are the maxilla and the 

 pre-maxilla of the same side connected ? Do you 

 find teeth on the pre-maxilla? At the posterior 

 end of the maxilla find the quadrato-jugal 

 bone. To what part of the skull is it attached ? 

 Lying ventrally from the squamosal, and towards 

 the median line from the quadrato-jugal, find the 

 pterygoid bone, composed of three branching 

 projections. With what does each projection ar- 

 ticulate ? 



Examine the under side of the skull, and find 

 the parasphenoid bone, forming the floor of the 

 cranial cavity. What is the shape of this bone ? 

 What is its relation to the auditory capsules? 

 Find between this bone and the fronto-parietal 

 of each side a foramen for the exit of the second 

 cranial or optic nerve. Examine the ventral 

 and lateral portions of the sphenethmoid, the 

 dorsal portion having been previously studied. 

 What is the shape of this bone ? Structure ? 

 Is the cranial cavity entirely enclosed by bony 

 structures ? Does the cranium show any trace 

 of segmentation? Compare in this respect with 



