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Show 1893.] DR. C. J. FORSYTH MAJOR ON MIOCENE SQUIRRELS. 199 the proportion is reversed. The Creodonta, with, on the whole, a simple type of molars, prevailing in the Puerco fauna, this fact has been considered as conclusive for Cope's theory, that the Mammalian molar is derived from a tritubercular type. Secondly, I cannot acknowledge that many of the Puerco molars said to be trituberculate, are really such; several species of Mio-clcmus, for example, showing a rather complex type. Now, considering the fact that we meet amongst the so-called trituberculate types with molars which really are septem-, octo-, and novem-tuberculate, it would have been more correct to speak of a triangular type, this shape of the outline being the only thing the molars in question have generally in common. But they are not all even triangular forms, as those presented by " Conoryctes" ditrigonus1, or Periptichus rhabdodon2, show on either side of the principal inner cusp two secondary cusps, and Riitimeyer has recorded similar types from Egerkingen. Moreover, Cope is not consistent with his own theory when he expounds his views as to the mutual relations of Creodonta3. The genus Mioclcenus, from which all the other Creodonta are said to be derived, possesses the most complex structure of molar of them all; whilst Mesonyx, whose upper molars present a simple tritubercular type, is placed at the end of a series instead of the beginning, as the theory would require. I further find inconsistencies in his diagram showing " the facts and hypotheses as to the phylogeny of the Mammalia"4. Here the Creodonta and Carnivora, as well as all the other placental Mammalia, with the exception of the Cetacea, are traced back by Cope to the Condylarthra. The latter, together with the Marsupialia, are derived from the Monotremata. This derivation implies that in the opinion of Prof. Cope the Monotrematous teeth must have been constructed on a trituberculate or a still more simple plan; and it may be remembered that when the first figures of worn teeth of Ornithorhynchus were published, they were proclaimed to support the tritubercular theory. But they are now known to be multituberculate; so I suppose that this being the case, the argument will probably be considered of no value, the Ornithorhynchus being an aberrant Protothere. But still the fact remains, and we must deal with it, that the only prototherian teeth known to this day are multituberculate to the extreme. If I a m not mistaken, the above views of Cope as to the mutual relations of the different orders of Mammals,-views which are in opposition with trituberculism,-show that their author is on his way, unconsciously perhaps for the present, to become a partisan of the multitubercular origin of Mammalian teeth, so that support 1 E. D. Cope, ' The Vertebrata of the Tertiary Formations of the West.-I.,' 1883, pi. xxiv. A. figs. 2, 4. 2 lb. pi. lvii. fig. la. 3 ' Synopsis Puerco Fauna,' p. 309. 4 E. D. Cope, " On the Evolution of the Vertebrates, progressive and retrogressive," Amer. Naturalist, February, March, April, 1885 (printed April 13, 1884), p. 347. |