464 Bulletin American Museum of Natural History. fVol. XX^^II, 



evolution has been a well nigh universal or only a frequent phenomenon. 

 In the former then such superordinal groups as the Cetacea may prove to be 

 unnatural, but in view of the net work of resemblances (p. 420) connecting 

 the different orders of the superorder with each other, it seems to be only a 

 conservative application of generally accepted principles to assume that 

 these resemblances imply derivation from a common source, and that in 

 general similar adaptations are most likely to arise in the descendants of 

 similar ancestors. 



A Classification of the Orders and Suborders of Mammals. 



Class Reptilia. 



Order Therapsida Broom. 



Suborder Dromosauria Broom. 

 Suborder Therocephalia Broom. 

 Suborder Anomodontia Owen. 

 Suborder Cynodontia (Owen) Broom. 

 Class Mammalia Linn. 



?Subclass Promammalia Haeckel. 



Order Protodonta Osborn. 

 Subclass Prototheria Gill, Huxley. 

 Order Monotremata Geoffroy. 

 Subclass Theria Parker & Haswell (= Eutheria Gill). 



I. Infraclass ]Metatheria Huxley. 

 Order Triconodonta Osborn. 



? Order Trituberculata Osborn (= Pantotheria Marsh, in part). 

 Order Marsupialia Illiger. 



Suborder Allotheria Marsh (Multituberculata Cope). 



Suborder Diprotodontia Owen. 



Suborder Paucituberculata Ameghino (Csenolestoidea). 



Suborder Polyprotodontia Owen. 



II. Infraclass Eutheria Huxley (Monodelphia Blainv., Placentalia 



auct.). 

 Superorder Therictoidea.^ 



Order Insectivora (Gray). 



Suborder Lipotyphla Hseckel. 



Section . Fam. Pantolestidse. 



Section Zalambdodonta Gill. Fam. Cente- 

 tidfe Potamogalidse, Solenodontidae, Nec- 

 rolestidae, Chrysochloridfe. 

 Section Erinaceomorpha. Fam. Leptictidse, 

 Erinaceidje, Dimylidte. 



' 0rp wild beast i'ktis "' weasel " (insectivore), elSrj form. 



