OBSERVATIONS ON THE DENTITION OF CHRYSOCHLORIS. 129" 



Some Observations on the Dentition of ChrysO' 

 chloris, and on the Tritubercular Theory. 



By 



R. Broom, D.Sc, M.D., C^I.X.S., 

 Victoria Colleo-e. Stelleubosch. 



With Plate II. 



The dentition of C h r y s o c h 1 o r i s differs so greatly from 

 tliat of most mammals that it has received a considerable 

 amount of attention. Unfortunately, specimens are so rare in 

 collections that workers have been much hampered, and have 

 sometimes been led to doubtful conclusions through having 

 only been able to examine a very limited number of imperfect 

 specimens. Much of the interest in the dentition centres in 

 the qiiestion of the molar structure. Cope considered that 

 the somewhat triangular molars represented a primitive type 

 not unlike that seen in some Secondary Mammals, and from 

 which all the later molar types have been evolved. This 

 view has been supported by Osborn, but in his recently pub- 

 lished work on the 'Evolution of the Mammalian Molar 

 Teeth' he apparently adopts the view of Gidley that the 

 molars of Chrysochloris are simplifications of the more 

 ordinary Insectivorous type, and that the '' trituberculy of 

 Centetes and Chrysochloris is a secondary acquirement 

 or pseudo-trituberculy." According to Gidley, the high main 

 cusp of the upper molars is a fusion of the paracone and 

 metacone of the ordinary type, and the small internal ledge is 

 the protocone. This is almost the same view as that sug- 



