76 THE OPOSSUMS. 



The Opossums may be at once distinguished from 

 other Mammalia, by the great number of their incisors, 

 of which there are ten in the upper jaw, and eight in 

 the lower 3 making together eighteen, which is two 

 more than is found in any other Marsupial animal, 

 and six more than are found in any placental quad- 

 ruped : they are arranged, in each jaw, so as to form 

 nearly a semicircle; in the upper jaw, the two foremost 

 incisors are larger than the rest, and generally separa- 

 ted from them by a small interspace their form is 

 nearly cylindrical, but at the apex they are slightly 

 dilated. The canine teeth are well developed, two 

 above and two below ; those in the upper jaw are 

 the larger ; behind the canines are seven molars on 

 each side of either jaw ; the three foremost of these, 

 in the upper jaw, are of a pointed and compressed 

 form, and possess each two roots, and thus present 

 the normal form of what are termed false molars ; 

 the next three molars on either side have each 

 three roots, two of which are external, and the third 

 is internal : the crown of each tooth presents a tri- 

 angular figure, and is tuberculous, the last molar has 

 also three roots, but its antero-posterior extent is 

 less. In the lower jaw there are also three false 

 molars on each side, and four true molars ; these 

 latter are strongly bristled with tubercles, have two 

 roots, and are of an oblong form. The roots of all 

 the teeth are remarkably long. The number of the 

 teeth may be thus expressed : 



Incisors, \; canines, |:j ; false molars, |:f ; true 

 molars, :=50. 



