54 AMPHITHERIID^E. 



the probability of the marsupial nature of the fossil : the 

 symphysial emargination (/), and the groove (e), are 

 characters common to the jaws of both genera, to which, 

 therefore, due weight must be assigned. And, if the 

 MyrmecoMus differs from the Amphitherium in the higher 

 position of the articular condyle (a), and the narrower coro- 

 noid process (5), it is, in other genera of the Marsupial 

 Order, as Thylacinus and Dasyurus, that the closest agree- 

 ment with Amphitherium is in this respect to be found. 

 The term Didelphys was originally applied to the Stones- 

 field Mammalian genus under consideration, in its wide 

 Linnsean 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 Thylacotheriwm, 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. 



