2G4: ANNALS NEW YORK ACADEMY OF SCIENCES 



Jurassic and Lower Cretaceous of England (Plagiaulax'^^) and Wy- 

 oming (Ctenacodon) . They again appear in the uppermost Cretaceous 

 and Paleocene of North America (Lance formation of Wyoming, Fort 

 Union of Montana, Puerco and Torrejon of Xew Mexico) and Europe 

 (Cernaysian) in the genera PtUodus, Neoplagiaulax, Poly mastodon and 

 Meniscoessus. They are questionably recorded in the Eocene Notosti/Iops 

 beds of Patagonia, in the genera Propohjinattodon , Polydolnps etc. (which 

 more probably belong to the same group as Ccvnolestes). They are not 

 known elsewhere except for part of a jaw from the middle Cretaceous 

 (Belly River) of Canada and a jaw {Karroomys) from the Jurassic 

 (Karroo beds) of South Africa. The front half of a skull long ago found 

 in the Karroo beds and described as Tritylodon is probably to be referred 

 to this group, although its mammalian nature has been questioned.'^' 



In addition to the Multituberculata, there are in the Jurassic and basal 

 Cretaceous of England and Wyoming a number of mammals with simpler 

 and more numerous teeth whose affinities are very imcertain. Whether 

 they are ancestral to marsupials, to placentals, to both or to neither is, 

 in the writei-'s opinion, an unsettled question. Its definite solution must 

 probably await the discovery of more complete material. 



In the uppermost Cretaceous (Lance formation) of Wyoming are foimd 

 in addition to teeth and jaw fragments of Multituberculata, a variety of 

 tritubercular teeth, some associated with fragments of the jaw. These 

 appear to be more definitely referable to the polyprotodont marsupials; 

 some of them may be quite near to the opossum. I have seen no evi- 

 dence among them of placental mammals, although most of them are too 

 fragmentary to exclude the possibility of the presence of Eutheria. 



The Paleocene fauna of New Mexico, Montana and France contains 

 numerous placentals and a few Multituberculata, but no polyprotodont or 

 true diprodont marsupials have yet been 23ositively recognized in it. It is 

 evidently not derived (except for certain of the Multituberculata) from 

 the fauna of the Lance formation. Yet it is almost, perhaps quite, con- 

 temporaneous with it and must be supposed to represent a distinct facies 

 of the fauna, differing in habitat from that of the Lance formation (the 

 Fort Union is ])artly intermediate). Polyprotodont marsupials certainly 

 persisted in North America and Europe, for we find the remains of 

 species nearly related to the existing opossums in the Lower and Middle 



'"^ lioUjihtn is a synonym of Plii(ii<iiiUi.r. tide (Jidloy. 



"Broom has recently made a careful rostudy of the atHuities of TiitiiUxlon. and con- 

 cludes that it is a mammal, but not closely related to the marsupials, and represents an 

 archaic specialization with many primitive ohai-acters inherited from the cynodont 

 reptiles. R. Broom : Trans. S. Af. I'hil. Soc. vol. xvi. pp. 7.3-77. 1905. Broc. Zool. 

 See. London. 1!)10. pp. 760-768. 1010. Bull. .\m. Mus. Nat. Hist., vol. xxxiii. pp. 115- 

 1.34. 1014. 



