THE SKELETON IN MAMMALIA. THE TEETH. 423 



The types of dentition characteristic of the different groups 

 of placental mammals may mostly be paralleled among 

 the Marsupials. Thus among the polyprotodont forms the 

 Didelphyidae or opossums, and some of the Dasyuridae, such 

 as Sarcophilus and Thylacinus, have a typical carnivorous 

 dentition with small incisors, large canines, and molars with 

 pointed compressed crowns. The dental formula of Tkylacinus, 



41 34 

 is i c T pin ^m -, total 46. 

 o 1 o 4 



In Myrmecobius five or six molar teeth occur on each side, 

 and the total number of teeth reaches fifty-two or fifty-six. 

 The teeth bear rows of tubercles, and resemble those of the 

 Multituberculate mesozoic Mammals 1 , more than do those of 

 any other living form. Calcified teeth have recently been 

 described 2 in Myrmecobius earlier than the functional or milk 

 set. This would relegate the milk teeth of mammals in general 



to a second series, and the permanent teeth to a third. In 



31-24 

 Notary ctes the dental formula 3 is given as i ^ c ^ pm ^ m ^ , 



total 40. The canines are small, and the anterior molars 

 have strongly developed cusps, and much resemble those of 

 Chrysochloris (Insectivora). 



Among the diprotodont types the Phascolomyidae, or 

 Wombats, have a dentition recalling that of the Rodents. All 

 the teeth grow from persistent pulps, and the incisors have 

 enamel only on the anterior surface as in Rodents. The dental 



formula is i | c |j pm ^ m^ , total 24. There are indications 



of a vestigial second pair of incisors. 



The Macropodidae, or Kangaroos, have a herbivorous 



O /A 1 \ 9 A 



dentition with the formula i - c ^ Q ' pm^m-^. The incisors 

 are sharp and cutting, and are separated by a long diastema or 



i See p. 348. 2 W. Leche, Morph. Jahrb. xx., pp. 113142 (1893). 

 3 E. C. Stirling, P. Z.S. 1891, p. 327. 



