作者：翟人杰

摘要：Changgindian Formation(=Changsintien Gravel, named by Hsieh,1933) is a thick series of tilted conglomates and red clays cropping our sporadically in the vicinity of Changxindian, some 20km S.W. of Beijing. For more than half a century the age of Changxindian Formation has been much debated. At first, it was regarded as of late Tertiary or early Pleistocene. From its tilted position and lithological character, J.G. Andersson (1923) compared it with Kuanchuang Series, Shantung Province in default of any fossil evidence. Yong Chung-chien(1934) based on a premolar of ungulate which determinated with hesitation as ?Eudinoceras sp., considered it to be of Epcene-Oligocene age. Late, Chow Minchen(1953) collected some fragments of mammal teeth as well as invertebrate remains. He briefly reviewed on the subject and reached the conclusion that the Formation is certainly early Tertiary in age. This conclusion which we considered beyond question is not generally accepted by the geologists.
    In the/Spring of 1976, a small collection was made by commune members at Gaodian, 1 km east of Changxindian. At least four distinct forms can be recognized in the collection. They are: Imequincisoria sp., a small fostercooperid; Hypsimylus beijingensis (gen.et sp, nov., vide infra)，an advanced eurymyloid; a miacid and a canid carnivores. On the basis of these fossils as well as  those definitely determinated by Chow (1953 )，some supplementary remarks on the age of Changxindian Formation are made and a late Eocene age is tentatively assigned to the fossil bearing beds in this paper.
    Hypsimylus beijingensis, represented by a fragment of left lower jaw and an isolated talonid of a milk premolar. The lower jaw is badly damaged and only a molar and a milk premolar are preserved after preparation. The crown of the milk premolar is rather low and with a well developed third lobe. It is similar to the imtermediate cheek teeth of Rhombomylus. The molar (M1) probably rootless or with only tiny roots. Though larger and much higher it is, the structure and relative location of lobes and grooves are essentially the same as that of Rhombomylhs. It is therefore suspected that Hypsimylus is probably a descendant of eurymyloid.

卷期：15卷 03期

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