1910.] Triconodonta and Trituherculata. 171 



. Cuvier examines the jaw later named .1 mphitherium prevostii, notes 



its resemblances to Didelphis and also its greater number of teeth. 



1818-1842. Controversy in regard to Mesozoic mammals. Buckland, 

 Prevost, Cuvier contend that the fossils in question are mammalian 

 and truly Mesozoic. De Blainville takes the opposing view that 

 they are reptilian. 



1838. De Blainville publishes his 'Doutes sur le ])retendu Didelphe de 

 Stonesfield,' urging that it showed evidence of a suture on the inner 

 side of the jaw and inferring that the jaw was composed of more 

 than one bone as in the Reptilia. This supposed suture was later 

 taken to be a mylohyoid groove and recently has been shown by 

 Bensley (1902) to have lodged the jMeckelian cartilage. 



1838. De Blainville proposes the name Amphithcrium prevostii {Didelphis 

 prevostii Cuvier MS.) in allusion to the supposedly ambiguous 

 nature of the remains. 



1842. Owen finally demonstrates the mammalian nature of the remains and 

 discovers that the molar teeth in Am.phitherium prevostii are of the 

 type now known as tuberculo-sectorial. 



1871. Owen monographs the Mesozoic Mammals and assigns the tri- 

 tuberculate insectivore-like genera Amhlotherium, Peralestes, Achy- 

 rodon, Peraspalax, Peramus and Sfi/lodoii to a division of the 

 Marsupialia (p. 111). 



1879-1880. Marsh discovers Upper Jurassic triconodonts and trituber- 

 eulates in North America and erects for them the order "Pantotheria" 

 (1880), holding that they cannot be placed satisfactorily in any of 

 the present orders, although recognizing the resemblances of certain 

 families to the Insectivores. 



1888. Osborn reviews and refigures all these animals and under the Tri- 

 conodontidfe of Marsh he groups the subfamilies Amphilestinse 

 Osborn, Phascolotheriinae Osborn, and Spalacotheriinse, which he 

 regards as primitive Marsupials. He includes the Stylacodontidse 

 and Amblotheriidse in a distinct suborder of the Placentals, the 

 "Insectivora Primitiva." He also attempts to trace in the orders 

 Protodonta, Triconodonta and Insectivora Primitiva the earlv 

 stages of the tritubercular type of medlars. 



1893. Osborn groups together the Amphitheriidae and x\mblotheriid9e 

 [Stylacodontidfie] under the name "Trituberculates" and suggests 

 that they are the Jurassic representatives of the Eutheria (Placentals). 

 He compares their tuberculosectorial molars with those of modern 

 Insectivores and says "they alone [of the Jurassic mammals] e.>diibit 

 the typical angular placental jaw" (1893, p. 204). 



