( 784 ) 



platyrrliiiies also, with llieir three preiiiohxry and iiiilkinuhxrs, possess 

 a reduced set of teeth, and indeed among the group, of the primitive 

 Primates which Osbokn puts together under tlie general name of 

 -\- Mesoilonta, forms are found with which both in upper and lower 

 jaw still four premolars occur (-f- Hyopsodus). According to the 

 investigations of Leche the number of four premolars has decreased 

 to three, because the premolar which follows immediately behind the 

 canine tooth — so the tirst or front of the row — has become lost. 

 As most convincing for this opinion of Leche the set of -|- JNJicro- 

 choerus may count, where only three premolars occur in the upper 

 jaw, and still aij many as four in the lo\ver jaw, but of these the 

 first of the row has been reduced to a rudiment without function. 

 Where it is as good as proved that the reduction of four to three 

 premolars with the primitive Primates has been brought about by 

 the disappearance of the premolar following immediately behind the 

 canine tooth, where moreover we know that with other animals also 

 reduction of teeth may take place in this spot, there it is quite 

 comprehensible that the further reduction of four to three premolars 

 in the same place is localized. The difference between the two 

 explained opinions is easily made recognizable by writing down the 

 complete tooth formula of the primiti\e Primates and that of the 

 now living ones. 



For the primitive Pi-imates we get the following formula in which 

 the probably original number of Inclsivi has not been reckoned with : 



/. 1. 2. C. 1. P. 1. 2. 3. 4. 



i. 1. 2. c. 1. m. 1. 2. 3. 4. M. 1. 2. 3. 



i. 1. 2. <■ 1. rn. 1. 2. 3. 4. M. 1. 2. 3. 

 I. 1. 2. C. 1. P. 1. 2. 3. 4. 



For the Platyrrhines (Cebidae) the formula becomes : 



/. 1. 2. C. 1. P. 0. 2. 3. 4. 



i. 1. 2. C. 1. m. 0. 2. 3. 4. M. 1. 2. 3. 



i. 1. 2. c. 1. m. 0. 2. 3. 4. M. 1. 2. 3. 

 /. 1. 2. C. 1. P. 0. 2. 3. 4. 



According to tlie opinion of Anthropologists this formula becomes 

 for the catarrhine Primates: 



I. 1. 2. C. 1. P. 0. 2. 3. 0. 



i. 1. 2. c. 1. m. Ü. 2. 3. 0. M. 1. 2. 3. 



i. 1. 2. c. 1. m. 0. 2. 3. 0. M. 1. 2. 3. 

 I. 1. 2 C. 1. P. 0. 2. 3. 0. 



