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Show 200 DR. C. J. FORSYTH MAJOR ON MIOCENE SQUIRRELS. [Feb. 28, seems to be coming to me from the very side from which it was least expected. Schlosser in his turn has, in his elaborate and valuable Monographs1, taken trituberculism as his guide for tracing the phylogeny of various orders of Mammalia. H e states his ground to be as follows:--" W e have but to start from the perfectly recognized primitive type and to trace the modifications which it has undergone" 2. This perfectly recognized primitive type is, according to Schlosser, the tritubercular type of upper molars, and the tuber-culo- sectorial type of lower molars. Accordingly, in the diagram placed by him at the head of the Monograph of Carnivora3, this form of molar type is attributed to the supposed first true Carnivore. In accordance with the theory, Schlosser considers Mesonyx or Sarcothraustes to be the primitive type of Carnivora *. With the same inexorable logic all Ungulates are derived from carnivorous Mammalia; the Condylarthra being considered as intermediate between the Ungulata and Creodonta5. I have not to deal with Carnivora on this occasion, so that I will only mention incidentally that, in m y eyes, amongst recent Carnivora, the Subursi (and, so far as the form of molars is concerned, Ailurus) approach nearest to the primitive carnivorous Mammalia, whilst some of the Aretocyonidse are the most primitive of Creodonta. Further objections may be made when Schlosser considers with Cope a rather complicated form of inferior molar-the tuberculosectorial type-to be a primitive form, and when it is assumed that, whilst the upper molars become further modified by addition, the lower molars from quinquetubercular become quadritubercular in progress of time, by the loss of an anterior cusp, the paraconid. The tuberculosectorial type is, in its turn, derived from a simpler 1 M. Schlosser, " Beitrage zur Kenutniss der Stammesgeschichte der Huf thiere und Versuch einer Systematik der Paar- und Unpaarhufer," Morpholog. Jahrbuch, xii. 1887, pp. 1-136 ;-id. " Die Affen, Lemuren, Chiropteren, Insecti-voren, Marsupialier, Creodonten und Carnivoren des europaischen Tertiars und deren Beziehungen zu ihren lebenden und fossilen aussereuropaischen Verwandten," I.-IIL, Wien, 1887-1890 (Beitrage z. Palaontologie Oesterreich- Ungarns, Bd. vi.-viii.);-id. "Leber die Beziehungen der ausgestorbenen Sauge-thierfaunen und ihr Verhaltniss zur Saugethierfauna der Gegenwart," Biolog-isches Centralblatt, Bd. viii. no. 19, Dec. 1888, pp. 582-631. - " Es handelt sich nur darum, von dem wohlerkannten Grundtypus auszu-gehen und aile Veranderungen zu verfolgen, welcher derselbe fahig ist," Die Affen. &c. ii. p. 9 (233). J Id. ib. p. 4 (228). 1 " W e n n wir von der Voraussetzung ausgehen-und hiezu sind wir audi vollauf berechtigt-dass der Oberkiefer-JMolar der Creodonta urspriinglich den Trituberculartypus in vollster Reinheit gezeigt habe, so miissen wir Mesonyx oder Sarcothraustes unbedingt als den ITrtypus betrachten, wenigstens fiirjene Formen, deren obere Molaren mit rundlichen Hockern versehen sind. Es schliessen sich diese Typen mehr an die Raubbeutler als an Bidelphys an," Die Affen, Lemuren, etc. i. p. 161. 0 ". . . es kann keinem Zweifel unterliegen, dass aile Hufthiere von Fleisch-fressern abstammen, wobei ehen die Condylarthren das Zwischenstadium reprasentiren " - M . Schlosser, Ausgestorbene Skugethierformen, I. c. p. 585. |