【摘要】 <正> 一、前人的工作 原牙形石Proconodontus属是J.F.Miller(1969)研究北美犹他州西部Notch Peak灰岩牙形石动物群的论文中提出来的,并于该属内建立了三个形式种,即P.muellert;P.notchpeakensis,P,carinatus。它们都是具有壁薄,基腔深而前后缘常发育棱脊的单锥型牙形石。在相应的地层中还见到Oistodus cambricus,O.minutus。Oistodus属的这两个种的标本在物质组成,颜色光泽以及体形轮廓方面与Proconodontus属的三个种更多还原

【Abstract】 Genus Proconodontus suggested by Miller has been proved to be a good mark for determining the geologic age of top Cambrian. Based on the study of some conodonts found in Xiaweidian district (west of Beijing) , the author proposed three main constituents for each species of Proconodontus i. e. symmetricus element, asymmetricus element and oistodontiform element. The three multielement species of Proconodontus are clearly distinguishable. Proconodontus muelteri: dark color, robuster and larger, with rather thick sheath, very deep basal cavity extending to cusp tip, no regeneration; Proconodontus cambrtcus: white color, compressed cusp, with thin sheath, deep basal cavity extending near cusp tip, little regeneration; Proconodontus notchpeakensis; white color, rather compressed cusp, with thin sheath,basal cavity extending only to cusp bend, noticeable regeneration above basal cavity.更多还原