72 MARSUPJALIA. 



strongly developed, and divided longitudinally by a pro- 

 minent ridge, the continuation of which forms the posterior 

 edge of the body of the tooth. At the base of the anterior 

 root of the tooth, the opening of a foramen is seen, on the 

 outer surface of the bone." 



In subsequently studying this fossil, I have not been 

 so satisfied as to its unequivocal indication of the genus 

 or family of the small zoophagous Mammal of which it 

 formed part. There is no tooth so little characteristic, 

 or upon which a determination of the genus could be less 

 safely founded, than one of the spurious molars of the 

 smaller carnivorous and omnivorous Ferae and Marswpialia. 

 A large, laterally compressed, sharp-pointed middle cone, 

 or cusp, with a small posterior and sometimes also a small 

 anterior talon, more or less distinctly developed, is the 

 form common to these teeth in many of the genera of the 

 above orders. It is on this account, and because the tooth of 

 the fossil in question differs in the shape of the middle, and 

 in the size of the accessory cusps, from that of any known 

 species of Didelphys, that I regard its reference to that 

 genus as premature, and the affinities of the species to 

 which it belongs as wanting further evidence, before they 

 can be determined beyond the reach of doubt. Besides 

 the presence of the anterior tubercle, or talon, and the 

 larger and more complicated posterior tubercle, the middle 

 compressed cone is more equilateral and symmetrical than 

 in the corresponding tooth of the Opossum. 



The crown of the premolars of the placental Fera, which 

 present the same general form as the fossil, are thicker 

 from side to side, in proportion to their breadth ; the pre- 

 molars of the Dasyurus, Thylacinus, and Phascogale, differ 

 in like manner from the fossil. It is in the marsupial 

 genera Didelphys and Perameles that the false molars pre- 



