258 MABST7PIAL1A. 



Genus TRICONODON, Owen l . 

 Including Triacanthodon, Owen 2 . 



The characters of the genus are those of the family. The discovery 

 of specimens of Triconodon mordax with four true molars has 

 shown that the so-called Triacanthodon is not separable. 



In the American Upper Jurassic a species of this genus is recorded 

 by Marsh 3 , the genus Priacodon being made for an allied form. 



Triconodon mordax, Owen 4 . 



Syn. (?) Triacanthodon serrula, Owen 5 . 



This is the type species ; the length of the space occupied by m71 + 

 m72 in the type specimen is 0,095, and that by mTT + m72 + in73 

 0,008. At least in many adult specimens there were four lower true 

 molars, but it is not improbable that in other examples n7T4 was 

 never developed. 



Hob. Europe (England). 



The following specimens (or their originals} were obtained from the 

 Middle Purbeck group of Durdlestone Bay, Swanage, Dorset- 

 shire. 



47766. The nearly entire left ramus of the mandible of a subadult 



(Fig.) individual, containing the anterior teeth and the first three 



true molars. This specimen (woodcut, fig. 38) is the type, 



Fig. 38. 





Tricatwdon tnordax.- The left ramus of the mandible (reversed) : from the 

 Purbeck of Swanage. \. 



and is figured by Owen in the Encyclopaedia Britannica,' 

 8th cd. vol. xvii. p. 161, fig. 86, and in his ' Mesozoic 

 Mammalia,' pi. iii. figs. 7, 7a. 



BecJcles Collection. Purchased, 1876. 



Encyclopedia Britannica, 8th ed. vol. xvii. p. 161 (1859). 

 Mesozoic Mammalia (Mon. Pal. Soc.), p. 72 (1871). 

 Amer. Journ. ser. 3, vol. xxxiii. p. 343 (1887). 

 Encyclopedia Britannica, loc. cit. 

 Mesozoic Mammalia, loc. cit. 



