14 



ding half way up the normal cusp (Fig. II e). It may be mentioned 

 that the second deciduous molar possesses it sometimes (Fig. II c). 



Pig. n. 



In Cynocephalus maimon a cusp exists on the 1. and 2. upper 

 molars in the groove between the anterior and posterior lingual cusps 

 which appears to represent this fifth cusp in man. To observe it in 

 its full development, however, it is necessary to study its condition in 

 the Carnivora. In Canis familiaris and vulpes (Fig. I c 5} it is large, 

 connected with and raised to nearly the same height as both lingual 

 cusps. In Meles taxus (Fig. I &5) it reaches what maybe considered 

 its maximum being prolonged anteriorly and posteriorly beyond the 

 other cusps and forming nearly onehalf of the tooth. 



We have seen in one human 1. upper molar a fifth cusp placed 

 on the buccal surface in connection with the antero-external cusp 

 (Fig. II f). In Cynocephalus maimon a similar cusp exists on the 

 buccal aspect of the third upper molar. 



Canines. The first-approach to a second cusp in these teeth is 

 a more than ordinary raising of the basal ridge in the upper canine, 

 a conditon which is not uncommon (Fig. II h). From this state of 

 affairs a cusp proper appears to be formed by two processes. Firstly, 

 a deepening of the cavity which appears when the basal ridge is ele- 

 vated and lies between the anterior and posterior parts of the crown, 

 occurs and is at least in part due to the disappearance of the rid- 

 ges normally connecting the point of the tooth with the basal ridge. 

 — Secondly, the basal ridge itself becomes itself further elevated. 

 This process attains its maximum by the formation of a second, di- 

 stinct, lingual, cusp causing the canine to assume the appearance of 

 a bicuspid. This is well shown in Fig. Ill Ca. Ca., which is a 

 sketch of an upper set of teeth peculiarly rich in supernumerary cusps. 

 Both first molars have the fifth lingual cusp, both canines have a se- 



