1888.] of Reptilian Character in Mammalian Teeth. 137 



As Sir Richard Owen has shown, these teeth in size, form, and serra- 

 tion are altogether like canines of carnivorous mammals. The molar 

 teeth of Theriodonts are usually but little specialised, and are small 

 and often simple cones. Even in Galesaurus the crowns of the molars 

 are compressed from side to side, and they have a central cusp no 

 more developed than in a lizard, with a smaller cusp on each side, 

 much as in some seals and porpoises, and as among porpoises there is 

 a long single root. 



Fig. 3. 



Molar and canine teeth of Galesaurus. — Brit. Mus., E. 845. The posterior teeth 

 are fractured, showing that the pulp cavity is closed at the base. 



An American genus, Empedias, from Permian or Triassic rocks, 

 referred by Professor Cope to a distinct order, the Pelycosauria, shows 

 an unusual specialisation of the molar teeth. They are compressed 

 from front to back, so as to have a great transverse extension on the 

 palate, which is absent from the premolars. There is a contraction 

 below the crown which is quite mammalian, and the root is single. 

 The crown may be described as having three cusps. The median 



Fig. 4. 



Transverse and superior views of molar tooth of JEmpedias.—Brlt. Mus., K. 613. 



central cusp is the most elevated, and is the only one which shows 

 evidence of wear, but the external and internal limits of the crown 

 are both elevated above the level of the concave spaces which divide 

 them from the middle cusp. Hence the tooth offers some evidence of 

 three cusps in parallel series as a reptilian character, and so far helps 

 to approximate reptilian and mammalian types. This dental con- 

 dition in Empedias has its chief interest in an approximation which 



