MARSUPIALS. 377 



Oxfordshire, of which the most instructive specimens are represented 

 in PL 99, figs. 1, 2, and 3. The first figure illustrates the dental 

 formula, which is remarkable for the number of the molars : 



Incisors — ; canines -— - ; premolars — ^ ; molars — -. 



3 — 3 1 — 1 ■*■ 6 — 6 6 — 6 



The incisors (i) are small, simple, and separated by intervals as in 

 the existing Marsupial genus Myrmecobius : the canine (I) appears by 

 its socket to have had a similar size and form. The shape of the 

 crowns of the premolars (p) and molars (m), is shown in the speci- 

 mens of the larger species {Amphitherium Broderipii, fig. 3) ; their 

 implantation of the jaw, each by two long slender roots, is demon- 

 strated by one of the specimens of the smaller species {Amphitherium 

 Prevostii, fig. 2). 



Genus Myrmecobius. — ^The only known existing representative 

 of this family is the animal described by Mr. Waterhouse, w^hich 

 constitutes the type of his genus Myrmecobius, and of which the 

 following is the remarkable dental formula, (PI. 98, fig. 4) : 



-r . 4—4 . 1—1 3—3 , 6—6 



Incisors — : canines — ; premolars — : molars — : = 54. 



3—3 ' 1—1 ' ^ 3—3 ' 6—6 



From this formula it will be seen that the number of true and 

 false molars, eighteen in both jaws, exceeds that of any other known 

 existing Marsupial, and nearly approaches the peculiar dental formula 

 of the extinct Amphitherium, as also that which characterizes some of 

 the existing Armadillos. The resemblance to the genus Dasypus 

 is further carried out in the small size of the molar teeth, their 

 separation from each other by slight interspaces, and their im- 

 plantation in sockets, which are not formed upon a well-developed 

 alveolar ridge or process. The molars (m), however, present a distinct 

 multicuspidate structure, and both the true and false ones possess 

 two separate fangs, as in other Marsupials. The inferior molars 

 are directed obliquely inwards, and the whole dental series describes 

 a slight sigmoid curve. The false molars (p) present the usual com- 

 pressed triangular form with the apex slightly recurved ; and the 

 base more or less obscurely notched before and behind. The canines 

 are very little longer than the false molars ; the incisors are minute. 



