56 AMPHITHERIID#. 
me soon after it came into his possession, and on being 
made acquainted with my wish, he kindly permitted me to 
take the requisite means to determine the shape of the 
angular process. The external surface, the only part ex- 
posed, was quite entire; and with a fine graving-tool, I 
cleared away sufficient of the matrix to show the extent to 
which it was imbedded. Although the inferior margin of 
the process is inflected so as to render the outer surface con- 
vex, the degree of inflection is less than in any of the 
known Marsupialia, and does not exceed that of the Mole 
or Hedgehog. This slightly inflected margin is broken 
away, in both the halftjaws that have their inner surface 
exposed, and if that indication of an inflected angle has 
been insisted upon too strongly as a marsupial character, 
we may be warned thereby to avoid the opposite extreme 
of concluding too absolutely, that a Mammal, with such 
peculiar dental characters as those of the Amphitherium, may 
not have combined the more essential pots of the Marsu- 
pial organization, with the lowest development of that 
peculiar character of the existing species, which is afforded 
by the angle of the jaw.* 
The main fact in the present inquiry,—the antiquity of 
the Mammalian type of organization,—is, if possible, more 
unequivocably established by the present than by the pre- 
ceding fossils. The whole outer surface of the ramus of 
the jaw is beautifully entire: not a trace of the alleged dis- 
tinct, deep fissures which, in Lizards and other cold-blooded 
Ovipara, separate the coronoid or complementary and other 
elements of the jaw can here be discerned. The broad and 
simple coronoid process shows the wide concavity and the 
* The ossa marsupialia even, may be absent, without the loss of the essential 
organic Characters of the Marsupial Order, as I have lately ascertained by dissec- 
tion of the great carnivorous Opossum (Thylacinus Harrisii) of Van Dieman’s 
Land. 
