358 
called the glyptodon. The occipital | fac of the skull slopes 
forward, from the plane of the occipital foramen, at an angle of 
45°, In the small existing armadillos it is vertical. In the glyp- 
todon this surface is divided by a medium vertical ridge, and 
es ogee from the upper surface of the skull by a transverse 
ridge. The interorbital part of the upper surface of the cranium 
is somewhat broad, and nearly flat, and concave at its posterior 
hal he anterior part of the base of the cranium, shows the 
large cavities of the olfactory bulbs, and the remains of an exten- 
sive cribriform process, evincing that the organ of smell was well 
developed. he existing species of this order of animals inhabit 
the warm and temperate parts of South America. It is char- 
acterized by the sloth, the ant-eater, and the armadillo. In their 
habits they are nocturnal and gregarious, burrow in the ground, 
~ and fe 
bodies, reptiles, the root of the manioc, and 
other succulent plants. Were this the only relic of the family 
that has been found in this part of the continent, it might seem 
presumptuous to deduce any special conclusion from its oc cur- 
rence in our tertiary beds. A single individual might, for orite; 
have wandered beyond the limits of its habitat, or by some acci- 
dental means have been transported into a foreign situation. But 
since other kindred remains of this family, the megatherium, for 
instance, have been found in this part of the continent, we ma 
reasonably conclude that it was once their proper abode, and 
zoologically connected with the southern division. What might 
have been its condition then, and what are the changes that have 
since occurred to have caused the present diversity of the two 
faunas, are s Kaien that force themselves upon our consideration. 
That this diversity has been produced by external physical 
causes, such as change of climate, and modifications of the earth’s 
- surface, can scarcely be doubted; for no other reason can be as- 
signed w why a living typical representation of these extinet spe- 
cies, should not still be found north as well as south of. the 
Mexican mp 
aphical distribution of faunas has changed since 
the a oi lived in the British isles, and the mastodon was in- 
digenous to both North and South America, ~ interesting facts 
to be accounted for in the adaptation of the nature and habits of 
animals to the external circumstances in which they are placed. 
Such an adaptation furnishes the reason of the limitation of the 
present congeners of our species to their South American locality- 
And we have only to suppose an assimilation of conditions be- 
tween the two parts of the contin ,and perhaps the substitu- 
tion of an unbroken connection by means of the continuation 0 
the table lands of Mexico, or the Carribean Islands, in order to 
= a similar correspondence between our _——— and extinct 
nas. 
