54 AMPHITHERID®. 
the probability of the marsupial nature of the fossil: the 
symphysial emargination (f), and the groove (¢), are 
characters common to the jaws of both genera, to which, 
therefore, due weight must be assigned. And, if the 
? 
Myrmecobius differs from the Amphitherium in the higher 
position of the articular condyle (a), and the narrower coro- 
noid process (4), it is, in other genera of the Marsupial 
Order, as Thylacinus and Dasyurus, that the closest agree- 
ment with Amphitheriwm is in this respect to be found. 
The term Didelphys was originally applied to the Stones- 
field Mammalian genus under consideration, in its wide 
Linnean sense, which is almost equivalent to the ordinal 
term Marsupialia. Three generic names, in the proper or 
restricted sense had been proposed in earnest, and a fourth 
in jest, for the ancient Insectivore, before its affinities were 
agreed upon, or its true dental formula known. In my 
Memoir of 1838, I ventured to observe, in reference to the 
new name proposed by M. Valenciennes, that it would 
have been more prudent to have chosen a less descriptive 
one than Thylacotherium, since the affinities of the fossil 
Insectivore to the marsupial order were indicated only with 
a certain degree of probability, and required further evi- 
dence before the desired demonstration could be attained. 
But the determination of the particular order of mammals 
to which the fossils in question belonged, was a matter of 
very inferior importance to the discovery of the class of 
vertebrate animals in which the species they represented 
ought to rank. In reference to this point the evidence 
afforded by the two jaws above described decisively proves, 
in my opinion, that they belong to a true, warm-blooded, 
mammiferous species, referrible also to the higher or 
unguiculate division of the class Mammalia, and to an 
insectivorous genus; with a probability of the marsupial 
character of such genus. 
