THE FROG. 195 



3. The hammer-shaped bone, which rests on the outer 

 edge of the prootic, and extends its " handle " down to 

 the posterior angle of the lower jaw, is the squamosal. 



4. On the dorsal surface, three pairs of bones in front 

 of the occipital meet on the median line. The first pair 

 consists of two long, narrow bones, which cover almost 

 the whole cranium. These are the parietofrontals. 



5. In front of the last lies a pair of triangular nasals. 



6. In front of the nasals is a pair of smaller bones 

 (premaxillaries) which form the tip of the snout, which 

 bear teeth, and which send narrow processes backward 

 toward the nasals. 



7. The border of the lower jaw is formed by the 

 mandible, which consists of two rami (or branches) which 

 meet on the median line in front. 



8. The greater part of the border of the upper jaw is 

 formed by a maxillary bone on either side, bearing abun- 

 dant teeth. 



9. Between the posterior end of maxillary and the 

 " handle end " of the squamosal is a small bone (the quad- 

 ratojugal~) which completes the border of the upper jaw. 



10. Looking at the ventral surface of the skull, a con- 

 spicuous T-shaped bone is seen extending along the floor 

 of the cranium. It is the parasplienoid. 



11. At its anterior end, a girdle bone (the sphenethmoid) 

 surrounds the anterior third of the brain case. 



12. Two slender palatines extend transversely outward 

 to the maxillaries on either side. These lie ventral to the 

 posterior border of the nasals. 



13. Between the palatines and the premaxillaries are a 

 pair of irregular vomers, each with a posterior process bear- 

 ing teeth. 



14. Lying just within the posterior angle of each jaw, 

 as seen from below, is a conspicuous, three-rayed bone 

 (the pterygoid). 



