386 MARSUPIALS. 



Pet. Taguanoides. The space between the tuberculate molars and the 

 procumbent incisor is occupied by four small teeth, of which the one 

 immediately anterior to the molars is large, compressed, pointed, and 

 has two roots ; the remaining three are rudimentary and have a 

 single fang ; the anterior of these corresponds to the one regarded as 

 a canine in the upper jaw. 



Among the species exhibiting this dental formula, viz. 



Incisors — : canines — : premolars — : molars — := 40. 



1—1 ' 1—1 ' ^ 3—3 ' 4—4 



are Pet. sciureus, Pet. Jlaviventer, and Pet. macrurus. 



The Pigmy Petaurist differs from the preceding and larger species, 

 in having the spurious molars large and sharp-pointed ; and the true 

 molars bristled each with four acute cusps. This tendency in the 

 dentition to the insectivorous character, with the modification of the 

 tail, induced M. Desmarest to separate the Pigmy Petaurist from the 

 rest of the species, and constitute a new sub-genus for its reception 

 under the name of Acrohates{Y) . Mr. Waterhouse first pointed out 

 that the Pigmy Petaurist had but three true molars on each side 

 of each jaw instead of four. (PI. 100, fig. 5). There seems, therefore, 

 to be better reason for accepting this sub-generic section, although 

 we evidently perceive a transition to this condition in the small size 

 of the hinder or fourth molars in the Sciurine Petaurist and its 

 congeners. 



The description of the dentition of the Pigmy Petaurist in the 

 ' Regne Animal,' besides the omission of this remarkable particular, 

 is not quite exact in other respects. In four adult specimens, two 

 of which were males, and two females with young in the pouch, I 

 find the following dental formula to be constant : 



Incisors — ; canines — : premolars — ^: molars — : = 36. 



3—3 ' 1—1 ' ^ 3—3 ' 3—3 



The three quadricuspid grinders of the upper jaw are pre- 

 ceded by three large premolars, each of which has two fangs, and 

 a compressed triangular sharp-pointed crown, shghtly but progres- 



(1) kKpoQ, summus, (iaivu, gradior, as frequenting the summits of trees. 



