250 MERISTIC VARIATION. [part i. 



shewn in the ordinary state. Lastly, in Pseudochirus behind the canine 

 there is a very small tooth, presumably p 1 , and between it and p* a 

 tooth of good size, presumably p s . 



Loiver jaw. In the front of the lower jaw there is on each side one 

 long incisor. Between it and the tooth corresponding to p 4 of the 

 upper jaw there are several small or "intermediate" teeth, whose 

 number varies greatly throughout the group. Thomas has made a 

 provisional attempt to find homologies for these small teeth, but in 

 view of the facts of their Variation it seems impossible to attribute 

 individuality to them and they will therefore be here merely numbered 

 from before backwards. 



Phalanger orientalis. In this species evidence will be 

 offered to prove the following facts : — 



(1) That between p^_ and p^_ there may be two small teeth, 

 one or both of which may perhaps represent p 3 ^ (Fig. 65). 



(2) That between p^ and the small p 3 there may be a 

 large tooth (Fig. 64, C), like the p 3 of Pseudochirus. 



(3) That p^ may be absent. 



(4) That in case of absence of p 3 , p 1 may be near to p^ 

 (Fig. 64, A). 



(5) That between the canine and p^_ there may be on one 

 side the usual large p]_, but on the other two teeth, evenly spaced, 

 each of about the proportions of p^ (Fig. 64, B). 



(6) That in the lower jaw the number of intermediate 

 teeth may vary from none to five, three being the most usual 

 number. 



372. Specimen having left side normal, one small premolar standing be- 

 tween P^ and F*. In the right upper jaw p] is normal and stands at the 

 same level as left p] ; p_ 4 is also normal in size, form and position (Fig. 

 64 C). In front of F 4 however there is a two-rooted tooth (marked y in 

 the figure) having somewhat the same shape as F 4 , but about |rds the 

 size. This tooth has not the form of the milk-predecessor of F 4 . A 

 small peg-like tooth (x in the figure) matching the small premolar 

 ("p 3 ") is also present, but is crowded out of the arcade and stands 

 internal to the tooth y. The lower jaw has three intermediate teetli 

 on each side. B. M., 1780, f. The form and position of the tooth y 

 suggest a comparison with the arrangement in Pseudochirus, in which 

 "F*" is in a very similar condition. In Fig. 64, D, a profile of Pseudo- 

 chirus is shewn, the dotted lines indicating the comparison suggested. 

 It will thus be seen that if the tooth y corresponds to p 3 of Pseudo- 

 chirus, the tooth x then has no correspondent. 



*373. Specimen (var. breviceps, Solomon Islands) having in right 

 upper jaw p 1 and p* but no "p a ": in left upper jaw p 1 stands at 

 a level anterior to that of right p 1 , and a small peg-shaped 

 tooth, "p 3 ," is present close to and almost touching p*. (Fig. 

 64, A) Lower jaw, right side, two intermediate teeth, of which 

 the posterior stands internal to ~p~* ; right side three intermediate 

 teeth. B. M., 1936,/ 





