FIG. 16.--Lower Jaw and Teeth of _Amphilestes broderipi_ (twice nat. size).]
It will be observed from the figures of the lower jaws, which are in most cases the only parts known, that in many instances the number of cheek-teeth exceeds that found in modern marsupials except _Myrmecobius_. The latter has indeed been regarded as the direct descendant of these Mesozoic forms; but as already stated, in the opinion of Mr B. A. Bensley, this is incorrect. It may be added that the division of these teeth into premolars and molars in figs. 14 and 16 is based upon the view of Sir R. Owen, and is not altogether trustworthy, while the restoration of some of the missing teeth is more or less conjectural. As regards the affinities of the creatures to which these jaws belonged, Professor Osborn has referred the _Triconodontidae_ and _Amphitheriidae_, together with the Curtodontidae (as represented by the English Purbeck _Curtodon_), to a primitive group of marsupials, while he has assigned the _Amblotheriidae_ and _Stylacodontidae_ to an ancestral assemblage of Insectivora. On the other hand, in the opinion of Professor H. Winge, a large number of these creatures are primitive monotremes. Besides the above, in the Trias of North America we have _Dromotherium_ and _Microconodon_, extremely primitive forms, representing the family _Dromotheriidae_, and apparently showing decided traces of reptilian affinity. It may be added that a few traces of mammals have been obtained from the English Wealden, among which an incisor tooth foreshadows the rodent type.
AUTHORITIES.--The above article is partly based on that by Sir W. H. Flower in the 9th edition of this work. See also O. Thomas, Catalogue of Monotremata and Marsupialia in the British Museum (1888); "On _Caenolestes_, a Survivor of the _Epanorthidae," Proc. Zool. Soc. London_ (1895); J. D. Ogilby, Catalogue of Australian Mammals (Sydney, 1895); B. A. Bensley, "A Theory of the Origin and Evolution of the Australian Marsupialia," _American Naturalist_ (1901); "On the Evolution of the Australian Marsupialia, &c.," _Trans. Linn. Soc._ (vol. ix., 1903); L. Dollo, "Arboreal Ancestry of Marsupials," _Miscell. Biologiques_ (Paris, 1899); B. Spencer, "Mammalia of the Horn Expedition" (1896); "Wynyardia, a Fossil Marsupial from Tasmania," _Proc. Zool. Soc. London_ (1900); J. P. Hill, "Contributions to the Morphology of the Female Urino-genital Organs in Marsupialia," _Proc. Linn. Soc. N. S. Wales_, vols. xxiv. and xxv.; "Contributions to the Embryology of the Marsupialia," _Quart. Journ. Micr. Science_, vol. xliii.; E. C. Stirling, "On _Notoryctes typhlops_," _Proc. Zool. Soc. London_ (1891); "Fossil Remains of Lake Cadibona," Part I. _Diprotodon, Mem. R. Soc. S. Australia_ (vol. i., 1889); R. Broom, "On the Affinities of _Thylacoleo," Proc. Linn. Soc. N. S. Wales_ (1898); H. F. Osborn, "Mesozoic Mammalia," _Journ. Acad. Nat. Sci. Philadelphia_ (vol. ix., 1888); E. S. Goodrich, "On the Fossil Mammalia from the Stonesfield Slate," _Quart. Journ. Micr. Science_ (vol. xxxv., 1894). (R. L.*)