SYSTEM OF NATURE. 
75 
invested with a hard and scaly shell, formed of little 
compartments like paving stones. This substance forms 
a shield over the forehead, another very large and convex 
over the shoulders, &c.” — C.R. A. We are indebted 
to Geology for disclosing some most remarkable animals 
allied to the armadilloes ; among these the genus Glyp- 
todon of Owen stands preeminent: in size it must have 
greatly exceeded any of its congeners, possessing a bulk 
much superior to that of an ox. The remarks of Dr. 
Lund on the extinct fauna of Brazil show that the arma¬ 
dilloes of former times were much more numerous not only 
in individuals, but also as regards species. There is a 
very close correspondence between this group and the 
tortoises, so obvious indeed as to have engaged the at¬ 
tention of many eminent naturalists. The remaining 
group of herpetoid placentals or ant-eaters exhibits a 
similarity to the lizards as striking as that of the arma¬ 
dilloes to the tortoises. The teeth in this tribe are 
remarkable for their variation in form, number and situa¬ 
tion, some of the genera having an unusual quantity, while 
others are entirely destitute of them. This character is 
also that of the class Reptilia. 
With regard to the relative position of the classes as 
proposed at page 70, little can be said; the respective 
sites of the subnormal and abnormal groups seem rather 
due to their correspondence with certain tribes of placen¬ 
tals, than to the existence of any chain of structural simi¬ 
larities inter se. I must not, however, be understood as 
saying that such a chain is non-existent. I only admit 
that it is unproven, and, in some instances, would be diffi¬ 
cult to prove, without a more severe analysis of structure 
and generation than the limits of an essay like the present 
