46 AMPHITHERinXE. 



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 Myrmecolius : and I have 

 observed a narrower impression extending forwards, from 

 the posterior entry of the dental canal, upon the inner 

 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 in 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 in 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 



* Loc. cit. p. 56. 



