256 THE AMERICAN NATURALIST. [Vor. XXXV. 
For Notoryctes Dollo describes a slight syndactylism and 
reduction of the second and third digits, which points out this 
form as still another offshoot of the main arboreal line. 
GENERAL REMARKS ON THE EVOLUTION OF AUSTRALIAN 
MARSUPIALS. 
When we compare the plan of evolution as determined by 
the structure of the teeth with that determined by the struc- 
ture of the feet, we note the fact that they practically coincide. 
Thus there are two lines leading from the prototypal forms, one 
of them showing an insectivorous-carnivorous and an arboreal- 
terrestrial evolution leading to the Dasyuridze, the other show- 
Dasyuridz Peramelidze ecu Phalangeridz : 
ee rous . 
ee orous Primitive Phalang- 
rial eride 
Myrmecobius ` 
y Td Phascolomyidze 
Y Properamelida(hyp.) 
gee tea oon 
real-térres strial 
Didelphyidze ? 
Prototypal forms [iiem 
ing an insectivorous-omnivorous and a progressive arboreal 
evolution leading to all the remaining marsupial families.. 
Following the former line, there appears to have been a 
typical evolution in all forms except Myrmecobius, which, as 
noted above, is probably degenerate in dentition. 
Following the omnivorous arboreal line, we find that one 
of its stages has been obliterated, being unrepresented among 
existing forms. The characters of other forms, however, leave . 
