AMPHITHERIUM. 53 



exceed the number usually found in the unguiculate Mam- 

 malia. The marsupial genus, Myrmecobius, (fig. 18,) has 

 nine molars on each side of the lower jaw, besides one small 

 canine and three conical incisors. 



Nat. size. 

 MYRMECOBIUS FASCIATUS. 



The teeth of Ampliitherium, moreover, differ from those 

 of DidelpJiys not only in number but also in size, being 

 relatively smaller. The teeth of Myrmecobius, besides their 

 approximation in number to those of AmpMtherium, re- 

 semble them in their small relative size more than do those 

 of Didelphys, but they are still smaller than in AmpJiithe- 

 rium, which in this respect, as well as in the structure of 

 the teeth, appears to hold an intermediate position between 

 Didelphys and Myrmecobim. The incisors (') of the 

 Myrmecobius are conical, separated at their base, diverging, 

 the anterior one almost as long as the canine (1) ; the first 

 three molars (p) have compressed, conical, bicuspid, or 

 tricuspid, crowns, the middle cusp being the largest, and 

 they have each two fangs ; they belong to the series of 

 premolars : the remaining six teeth are multicuspid and 

 true molars, as in Amphitheriwn. 



The discovery of an existing quadruped in the marsupial 

 series, presenting so many resemblances in the number, 

 size, shape, and proportions of the teeth, to the AmpMthe- 

 rium, so far as the dental characters of that genus are 

 elucidated by the two specimens above described, adds to 



