172 Bulletin American Museum of Natural History. [Vol. XXVII, 



1893. Osborn (in Zittel's Pala?ontolog'ie) substitutes the monomial term 

 Trituberculata for Insectivora Primitiva and now includes in the 

 group the families Amphitheriida?, Amblotheriidse and Stylacodonti- 

 dje. He assigns the Triconodontidjie to a new order, the Trieono- 

 donta. 



1894. Goodrich contributes a valuable article, " On the Fossil Mammals 

 from the Stonesfield Slate" in which he redescribes and gives careful 

 figures of the types of the species of Amphitherium, Amphiti/lus, 

 Amphilestes Phascolotherium. 



1907. Osborn (1907, pp. 18-23) further revises the classification and brings 

 together many new and old figures of specimens. 



Special interest of these Mesozoic Orders. 



Nearly a century has elapsed since the geologist Broderip received from 

 the hands of "an ancient stonemason" two small fragmentary jaws from the 

 Stonesfield Slate which were the means of overthrowing the dogma that 

 "no mammals occur in the INIesozoic." Notwithstanding the later array of 

 generic and specific names of Mesozoic mammals, these minute jaws and 

 teeth still retain some of the ambiguous meaning which was signalized in the 

 name AniphitJierium, inasmuch as they oft'er suggestions, rather than proof, 

 of relationship to different groups of mammals. 



Yet the few positive facts which they have yielded, when viewed against 

 the general background of palseontological knowledge, appear as important 

 landmarks in mammalian history. Standing in geological time between the 

 partly-known reptilian ancestors of the mammals and the better known faima 

 of the Tertiary, these Mesozoic orders include certain members which so 

 far as the scanty evidence indicates were also more or less intermediate 

 in structure. In certain features they retain reminiscences of more ancient 

 types, in others they foreshadow the Polyprotodont Marsupials and Insecti- 

 vores of a later period. 



The Triconodonta. 



The Triconodonts as described by Owen, Osborn and INIarsh are known 

 from the Stonefield Slate and Middle Purbeck (Middle and Upper Jurassic 

 respectively) of England and from Marsh's "Atlantosaurus Beds" (Morri- 

 son formation) of Wyoming. The order as defined by Osborn (1907, pp. 

 21-22) includes the genera Amphilestes, Phascolotherium, Triconodon, Pria- 

 codon, Tinodon, Spalacotherium, Mcnacodon and Peralestes, all known chiefly 



