OF THE AUSTRALIAN MAESUPIALIA. 



105 



show signs of Laving been so at an earlier stage. It is interesting to note tliat a similar 

 lack of differentiation characterizes the homologous teeth in tlie Peratnelidce (tig. 2, e). 

 The lateral incisors present a cm-ious appearance, due to a subcaniniform. modification 

 of their tips. This condition is only an extreme development of that seen in the 

 DasyurinEB and Didelphyidae (fig. 2, g), Avhere the tips of the lateral teeth are ah'eady 

 acute and directed slightly backwards. A very similar appearance to that seen in 

 Myrmecohius has been figured by Flower and Lydekker (1891, p. 539) in the degenerate 



FiK. 2. 



The antemolar teeth of Myrmecohius fasciatus compared with those of other Marsupials. 

 a-c. Myrmecohius, upper and lower dentition of normal specimens; d. Lower dentition of abnormal specimen with 

 four lower incisors ; e. Perameles o6csm?«, upper incisors; f. Vlunropas castanotis, upper incisors and c:iniiu' ; 

 g. MetacMrvs opossum, upper incisors and canine. Abbreviations : ('., incisors ; en., canine : p., premuUirs ; 

 m., molars. 



carnivore Uupleres, and a similar tendency towards a posterior extension of the tips of 

 the lateral teeth is found as a secondary character in certain of the Peramelidte (fig. 2, e). 

 All of the lower incisors tend to be caniniform. Their contour is much less an 1411 la r 

 than in the upper teeth, and a similar difference is observable in normal forms. 'I'he 

 median lower incisors are slightly enlarged, as in Phascoyale penicilluta *. 



Canines. — These teeth show a distinct departure from the usual type found in tlie 

 "Dasyuridse, this being particularly the case with the iipper ones. The latter (fiy. '1, b) 

 tend to be laterally compressed, and in some cases present accessory anterior and 

 posterior cusps. In addition, they sometimes show a grooving of tlie root. 'I'liese 

 characters give them an almost premolariform appearance, and this is lurther enhanced 

 by the fact that there is a gradual reduction in size of the cheek-teeth proceeding from 

 the canine to the posterior premolar. 



The fact that morphologically the canines are modified premolars might at first siglit 



* The incisors of Myrmecohius, like all of the remaining teeth, tend to be 8e[)arated by diastemata, and llau 

 ]iresent an appearance not unlike that seen in certain of the Meso/.oic Mammalia. The condition is, however, a 

 purelj' secondary one, and is due to the elou_ij;ation of the mu/zle common to this and other ant-eating mammals. 

 It is interesting to note that even the comparatively advanced young show no indications of the elongated muzzle 

 characteristic of the adult, the facial region presenting a curioua abbreviated appearance, which Leche has aptl\ 

 referred to as " cine wirkliche Mopsform." 



