46 AMPHITHERIID &. 
linear fissures, penetrating the substance of the bone ; but 
the bottom of the groove in the jaw of the Amphitherium 
is quite entire, and the decreasing breadth of the groove 
indicates its origin from the pressure of a nerve or vessel. 
A similar but relatively wider and shorter groove im- 
presses the same part of the lower jaw in the insectivorous 
marsupial quadruped called Myrmecobius: and I have 
observed a narrower impression extending forwards, from 
the posterior entry of the dental canal, upon the iner 
surface of the ramus of the jaw in the Wombat (Phas- 
colomys), another Mammal of the Marsupial order. 
The following is the exact condition of the teeth, in this 
much-referred to specimen of Amphitherium: there are ten 
molars im situ, the seven anterior ones imbedded by two 
long and slender fangs in deep and distinct sockets. The 
molars gradually increase in size from the foremost to the 
sixth, in the present specimen: the rest are equal, except 
the last, which is somewhat smaller. The nearly perfect 
specimen of the jaw of the Amphitherium im the collec- 
tion of Dr. Buckland, lately discovered and figured at 
the head of the present chapter (fig. 15), has demon- 
strated the accuracy of my deductions from the less 
complete specimen described in the Geological Trans- 
actions,* viz. that the Amphitherium had sixteen teeth in 
each ramus. Of the ten teeth, contained in the fossil under 
consideration, the first four, counting backwards, corres- 
pond with the third, fourth, fifth, and sixth premolars, and 
the remaining six to the true molars; the crowns of the 
fourth, fifth, and sixth premolars, enumerating them ac- 
cording to the true dental formula of the genus, are entire, 
and shew them to be simple, compressed, consisting of a 
single or principal conical cusp, with a minute tubercle or 
SMOCHelt aps ko Os 
