70 J. D, Dana on the Classification of Mammals. 
aGevos). Judging of the mean size of the life-system in the two 
divisions from their more active as well as powerful species, the 
lineal ratio is not far from 4:1, as between the Decapods an 
Tetradecapods. 
The orders in these two groups, the Microsthenes and Megas- 
thenes, have throughout a precise parallelism. “The Bais or 
Chiropters in the latter represent the Monkeys or Quadrumanes 
in the former, these orders having so close relations that they 
are made to follow one another in Cuvier’s system; the Jnsecti- 
vores represent the Carnivores; the Rodents represent the Her- 
bivores; and the Brutes or EHdeniaies, the Mutilates. 
The classification indicated is then as follows: 
I. Arcnont1a (vel Dreopa)—Man (alone). 
Il. MecastHena. LUI. MrorosrHena. 
1, Quadrumana 1. Cheiroptera 
2. Carnivora. 2. Insectivora. 
8. Herbivora. 8. Rodentia. 
4, Mutilata. 4, Bruta (Edentata.) 
IV. Odricomea. 
1. Marsupialia. 
2. Monotremata. 
It is interesting to observe, also, that the four orders of Megas 
thenes rise in grade, from the 4th to the 1st, on the principles 
cephalization stated; and this affords other evidence, super 
to that of higher importance based on difference in_ type of 
structure, as to the naturalness of these subdivisions. The spe 
cies of the 4th—the Mutilates—are characterized by a degrada 
tion and partial obsolescence of the limbs; by the body <a 
massively prolonged behind; by a large part of the elongate 
vertebral column being used for locomotion; by the form an 
the low grade of structure of the head; and by the teeth, al- 
ways of extreme simplicity of form, in most species of one 
ly, in some excessively multiplied in number, in others 3° 
wanting ;—peculiarities indicating a very low degree of cephaliz 
