KANGAROOS. 391 



originally applied by Illiger to the Kangaroos general]y(l). The other 

 Kangaroos are characterised by M. Fr. Cuvier under the generic term 

 Macropus, by the following dental formula : — 



Incisors - : molars — : = 24. 



2 ' 4-4 



The truth, however, is, that both the Halmaturi and Macropi of 

 M. Fr. Cuvier have their teeth developed in precisely the same 

 number and manner : they only differ in the length of time during 

 which certain of these teeth are retained (2). In the great Kangaroo, 

 for example, the permanent premolar which succeeds the corre- 

 sponding deciduous one in the vertical direction, is pushed out of 

 place and shed by the time the last true molar has cut the gum : 

 the first true molar is soon afterwards extruded ; and I have 

 seen a skull of an old Macropus major in the Museum at Ley den, 

 in which the grinders were reduced to two on each side of each 

 jaw by this yielding of the anterior ones to the vis a tergo of their 

 successors. 



Remains of gigantic Kangaroos have been discovered in the 

 same caves in Australia which contained the teeth and jaws of the 

 large extinct Dasyurus laniarius, and they probably formed the prey 

 of that species and of its contemporary the Thylacine, which has 

 equally become extinct in the continent of Australia. 



Portions of the lower jaw and teeth of two of these extinct species 

 of Kangaroos are figured of the natural size in Plate 101. They are 



(1) Prodromus Systematis Mammalium et Avium, 8vo. 1811. The dental character which 

 this excellent naturaUst gives, accurately expresses the condition of the canine or laniary 

 teeth, " Laniarii aut nulli, aut superiores 2 ambigui, minuti, in medio inter primores et 

 molares coUocati," p. 80 ; but there are never more than five molars in place on each side of 

 each jaw in the Kangaroo, 



(2) M. Fr. Cuvier was aware that a deciduous false molar existed in the great 

 Kangaroo and other species of his subgenus Macropus, but he believed that it was peculiar 

 to an early period of life, and then existed only in a rudimental state, or " en germe ;" and 

 that instead of being displaced and succeeded in the vertical direction by a permanent 

 false molar, as in the Halmaturi, it was displaced by the true molars, which are de- 

 veloped from behind forwards. I have, however, detected the crown of the permanent 

 false molar in the jaws of the Macropus major in a concealed alveolus, and have observed 

 it completely formed and in place in an individual which had nearly attained its full size. — 

 See M. Fr. Cuvier's account of the Halmaturus Thetis in the " Histoire des Mammiferes" 

 foUo. 



