135 



siderably from the jaw. It is placed somewhat obliquely in the 



mandible, so that it points inwards to a certain degree. Had the 



obliquity been absent, and had the crown been subjected to the amount 



of wear usual in a last molar, the size of the wearing surface and 

 the "pattern" thereon would have been exactly those of the normal 

 ast molar. 



Fig. 2. pm^ second premolar (position of), m* supernumerary molar. 



These cases offer several features of much interest. In the first 

 place it is to be- observed that the second last tooth (normally the 

 last) does not differ in any material respect from the tooth normally 

 present in the same position in the dental series. In the case I have 

 already recorded (3) the supernumerary molar had the form and size 

 of the normal last molar — as is the case with the teeth now de- 

 scribed — but the second last molar (m^j resembled the normal second 

 last normal (m-) ; thus illustrating a hypothesis enunciated by Bate- 

 son (6). This writer has stated it as a rule that if, in those dental 

 series in which the last tooth is normally small, an additional tooth 

 be present at the posterior end of the series, the normally ultimate 

 tooth (which has of necessity l^ecome penultimate) takes on the 

 characters of the normal penultimate. From an examination of my 

 three cases, it is obvious that in the horse, in which animal the 

 normal last tooth is not small, there may or may not be an alteration 



