Abnormal Dentition in a Dhole. 197 



distinct diastemata. This arrangement is disturbed on the 

 right side by the presence of the supernumerary tooth. The 

 axis of pm 2 is inclined slightly forwards and inwards, that of 

 pm 3 slightly forwards and outwards, so that the two axes if 

 continued would cut one another at an obtuse angle of about 

 135°. The two teeth are separated by a comparatively wide 

 diastema, in which towards the inner side is wedged the 

 supernumerary tooth, the axis of which is longitudinal, not 

 oblique ; its crown slightly overlaps in front the posterior 

 portion of the crown of pm 2 and behind the anterior portion 

 of the crown of pm 3 , and touches them both. The area 

 between pm 1 and pm* on the left side is practically the same 

 length as that on the right side, namely 20 mm. ; but the sum 

 of the two teeth, pm 2 and pm 3 , on the left side is 17 mm., while 

 that of the corresponding teeth + the additional tooth on the 

 right side is about 19 mm. The three teeth therefore are 

 spread over a rather larger area than the two premolars of 

 the left side, and this is gained by encroachment upon the 

 diastemata separating pm 1 and pm 2 and pm 3 and pm 4 . There 

 is no noticeable disparity in size between the normal pre- 

 molars of the right and left mandibles. 



Apart from the interest of the occurrence of this abnormality 

 in the lower jaw, I am unable to find a parallel to it in the 

 many instances of abnormality in the premolar dentition of the 

 upper jaw in the Canidae cited by Mr. Bateson. In most 

 cases, both in wild species and in domestic dogs, where 

 additional premolars are recorded there are two premolars 

 resembling the normal pm 1 between the canine and pm 2 . 

 Perhaps the nearest approach to the above-described variation 

 in Cuon dukhunensis is presented by the skull of a specimen 

 of the black-backed jackal (Cants mesomelas) (no. 228 of 

 Bateson), which showed on the right side a supernumerary 

 tooth inside the upper pm 3 , and closely resembling it, though 

 a little smaller. But, as has been stated, the supernumerary 

 tooth in this skull of Cuon dukhunensis differs both from pm? 

 and pm 3 in the shape and size of the crown and also of its 

 roots. 



In this connection arises another interesting point. In the 

 skull of Cuon dukhunensis under discussion the roots of pm 2 

 of the lower jaw are fused — or, to put it another way, not 

 divaricated, either on the right or the left side. But this 

 feature is, I think, abnormal in the genus, for I find that in 

 two other skulls of this species as well as in one of a Siberian 

 dhole (Cuon alpinus) the two roots of this tooth are quite 

 distinct from base to point and resemble not a little in shape 

 and direction the roots of pm 3 of all the dholes' skulls 



