246 MERISTIC VARIATION. [part i. 



*358. Ass : thoroughbred Spanish she-ass, in the Museum of the Royal 

 College of Surgeons, has a large supernumerary molar on each side in 

 series in the upper jaw, and a similar tooth in the left lower jaw. The 

 same skull has the first premolar also present on each side in the upper 

 jaw, as is not unfrequently the case in Equidse. All four canines are 

 present as minute teeth. The dental formula for this skull is therefore 



,3_3 l_i 4_4 4 — 1 tK 

 ^3=3 C r=Ti^3=3 m 4^3 =45 ' 



359. Auchenia lama : specimen having a suj>ernumerary (fourth) 

 molar in the lower jaw [? on both sides]. This tooth was fully formed 

 and resembled the normal last molar. In the upper jaw T was a small 

 alveolus behind ?/i 3 , for another tooth which was not present in the 

 specimen. Rutimeyer, L., Vers, einer nattirl. Geschichte des Binder, 

 Zurich, I. p. 55, Note. 



360. Cervus axis $ : specimen having a supernumerary grinder placed 

 on the inside of the normal series on the left side of the upper jaw. 

 In the lower jaw of the same specimen the following supernumerary 

 teeth : (1) a small, compressed accessory tooth on both sides placed 

 internally to m? ; and (2) behind the large three-fold sixth molar was a 

 smaller two-fold tooth which had caused a displacement of the 6th 

 molar. Donitz, Sitzungsb. d. naturf. Fr., Berlin, 1872, p. 54. 



361. Cervus rufus : having supernumerary (4th) premolar on one side 

 in lower jaw. Hensel, Morph. Jahrb., v. p. 555. 



362. Ox : supernumerary upper molar on left side. Magitot, I. <?., p. 

 106. 



Sheep : extra molar in left lower jaw, ibid., p. 105, PI. v. fig. 10. 

 [? some error ; the figure represents a normal jaw.] 



MARSUPIALIA. 



The facts given in illustration of Variation in the dentition 

 of Marsupials relate only to a part of the subject and to selected 

 forms. Some of the cases to be given are however of exceptional 

 importance. Evidence is offered in reference to the following 

 subjects: 



(1) Incisors. 



(2) Premolars, and the "Intermediate" teeth (in the lower 



jaw), of Phalangerida3. 



(3) Premolars and Molars of Dasyuridaa and Didelphyidre. 



(4) Molars of certain Macropodida?. 



(1) Incisors. 



The following cases of Variation in incisors are all that were 

 met with in the Marsupials examined. 



Didelphyid/E : incisors normally f, thus differing from the Dasy- 

 uridpe (i |) with which they have much in common 1 . Of various 



1 Thomas states that the family Didelphyidae "is, on the whole, very closely 

 allied to the Dasyuridae, from which, were it not for its isolated geographical 

 position, it would be very doubtfully separable. " Cat. Marsup. Brit. Mas., 1888, p. 315. 



