ISOPROEDRIUM 85 



down in that region. Pm. I is represented by a moder- 

 ately large alveolus, 10 mm. long. Pm. 2 is 13 mm. long 

 by 10 mm. wide, and slightly constricted medianly as far 

 as the enamel is concerned, the furrow in either side being 

 filled with cement. Pm. 3 is 18 mm. long by 12 wide and 

 similar. There is only an alveolus for pm. 4, which is 

 23 mm. long. M. I is incomplete, but was about 23 mm. 

 long by 10% mm. wide and is distinguished by the deep 

 outer inflexion. Each tooth present is covered with a 

 heavy layer of enamel nearly a millimeter thick; and each 

 of the teeth is unique in that the enamel is wanting on 

 the anterior internal and the posterior internal corners of 

 the teeth. 



