3. Skull high — height at least half the width; with a bony palate before 



and partly underlying the floor of the brain case 



Mammals (See chapter 15) 

 Skull flat — height not more than onc'fifth of the width; with a bottle 

 or dagger'shaped bone forming a large part of the under side 



Amphibia 4. 



4. With a gap between the end of the upper jaw and side of cranium, or 



with a short row of teeth in the center front of a complete row on 



upper jaw; processes on which the lower jaw is hung slanting forward 



Salamanders 



With a bar joining the end of the upper jaw to the side of the cranium; 



processes on which the lower jaw is hung slanting backward 5. 



5. With teeth on the upper jaw 



Frogs and Spadefoot Toads 

 No teeth on the upper jaw 

 Toads 



6. Brain case almost spherical, the bones fused together so that their sutures 



are not visible; orbits (eyc'sockets) very large, about one-third of the 

 total length of skull; jaws elongated to form a beak 

 Bnds 

 Brain case flattened or angular; sutures usually visible; orbits seldom 

 more than one-fifth of the total length of skull; jaws not beak-like, or 

 else with a sharp ridge on back of skull 7. 



7. No evidences of teeth; bones of skull, except lower jaw, apparently all 



joined immovably together; with a sharp central crest on back of top 

 of head 



Turtles 

 Teeth present; no prominent crest on back of skull 8. 



8. Skull long, wide and flat; bones solidly joined; teeth peg-like, set in 



sockets 



Alligator 

 Skull not especially long, wide and flat; bones suspending the lower jaw 

 somewhat movable or hinged to others; teeth needle-like, fused to the 

 top of the inner edge of jaw bone 9. 



9. Bones of brain case solidly joined, but almost all others hinged; usually 



with two rows of upper teeth, the inner row as long and well dc 

 veloped as the outer row 



Sna\es 

 Bones suspending lower jaw hinged, but the others fixed in position; a 

 small opening usually present in the top center of the brain case 



Lizards 



26 



