30 DR. J. MURIE AND MR. A. D. BARTI.ETT [Jan. 9, 



cutting-edges of the outer and inner sides of the lower incisors, and 

 justly attributed to the closing of the lower upon the upper jaw with 

 the separation of the lower incisors the effect of producing closer 

 contact between the cutting-edges of both jaws upon one another, yet 

 he has failed to notice the use, and mode of application of the inner 

 cutting-edges of the lower incisors. 



Professor Owen, in his valuable memoir " on the Osteology of the 

 Marsupialia," in the 'Transactions of the Zoological Society,' 1841, 

 vol. ii. p. 394, does not mention anything from which it would be 

 inferred that the lower incisors are used in the maimer we have de- 

 scribed ; he says, however, among other things, that, excepting the 

 Koala, " in all the other marsupial crania which I have examined, 

 the rami of the lower jaw are not anchylosed at the symphysis." 



Having satisfied ourselves of the occurrence of the mobility of the 

 teeth and symphysis of the lower jaws in the living animals, it became 

 an object of interest to ascertain in the dead ones how this was pro- 

 duced ; and for this purpose we commenced by studying the bones 

 in a few macerated skulls. 



In one of these, an adult specimen of Macropus major (M. gig an- 

 iens), the two halves of the inferior maxilla of which have been com- 

 pletely separated, when the symphyses are applied closely together 

 the two lower incisors are approximated at their anterior half or 

 points upon the inner edges ; while the posterior halves of tbe inci- 

 sors have an interval of nearly one-eighth of an inch, of a somewhat 

 spear-shape. The two margins of the incisors in apposition are worn 

 and flattened, evidently by the continued attrition of the one upon 

 the other. The symphysis of the bones at the part where they are 

 most closely applied is at the posterior half; and there they unite, 

 though loosely, by an articulation in the manner of a diaphysis. 



In a Macropus ocydromus the symphysis and teeth of the man- 

 dible exhibit very nearly the same appearances. 



The same parts in Osphranter antilopinus differ in the anterior 

 and inner cutting-edges of the incisors not coming together so sharphy, 

 by reason of the points being more rounded and set outwards than 

 in the two former species. When the teeth are separated there is an 

 open space of fully one-eighth of an inch ; there is also a diminutive 

 ovate space at their base, which may in part be a natural deficiency; 

 but likewise the dental tissue seems partially abraded as if worn by 

 the action spoken of, possibly by the tearing of grasses or other, 

 harder stems. 



The shape and position of the incisors of Halmaturus agilis ap- 

 proach those of Macropus major; the interval at the base of the teeth, 

 however, is relatively wider and correspondingly shorter than in that 

 larger species. 



Halmaturus irma presents no remarkable difference from Ma- 

 cropus major, excepting in the mandible being less in dimensions, 

 and consequently having a smaller separation of the teeth. 



Besides an examination of the dried bones, we have been fortunate 

 in having the opportunity of studying the appearances in two animals 

 which have recently died in the Gardens. In one of these, Bennett's 



