SYSTEMATIC ARRANGEMENT 29 



NOTUNGULATA 



Order 1. Upper molars composed of an external longi- 

 tudinal crest and two transverse crests, the posterior the 

 less developed; lower molars composed of two joining cres- 

 cents with a "pillar" in the posterior crescent; structure 

 of the feet and limbs varying. 



Suborder 1. Litopterna: teeth brachydont to hypsodont; 

 lower molars with the anterior and posterior cres- 

 cents subequal; squamoso-periotic region not in- 

 flated; limbs elongated; pes unguligrade; digits 3-3 

 or 1— 1. 



Suborder 2. Typotheria: teeth hypsodont lower molars 

 with the anterior crescent shorter than the poste- 

 rior; squamoso-periotic region inflated; limbs 

 elongated in varying degrees; pes plantigrade to 

 semi-plantigrade; digits 5-4 or 4-4. 



Suborder 3. Toxodontia: teeth brachydont to hypso- 

 dont; lower molars with the anterior crescent shorter 

 than the posterior; squamoso-periotic region in- 

 flated; limbs short; pes semidigitigrade to digiti- 

 grade; digits 3-3. 



Suborder 4. Homolodontotheria : teeth brachydont; 

 lower molars similar to those of Toxodontia; limbs 

 moderately elongate; pes semidigitigrade; digits 

 with large curved claws, 5-5. 



Suborder 5. Astrapotheria : teeth brachydont to mod- 

 erately hypsodont; canines enlarged into tushes; 

 molars similar to those of Toxodontia; limbs greatly 

 elongated; feet unknown. 



PROBOSCIDEA 



Order II. (see page 68) 



Suborder 1. Pyrotheria: incisors developed into tushes; 



molars bilophodont; limbs short, especially the 



lower element; feet digitigrade. 



