THE THECAL STRUCTURE OF MONOCLIMACIS? GALAENSIS

Authors

  • BARRIE RICKARDS

    1. Department of Geology, Trinity College, Dublin 2. Author's address after October 1968: Department of Geology, Sedgwick Museum, Cambridge, England.
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Abstract

Monoclimacis? galaensis (Lapworth), a biform Llandoverian graptolite, is interpreted as having proximal thecal ‘hooks’ composed of paired lateral lappets, and lacking retroversion of the dorsal thecal wall. A parallel is drawn between M? galaensis and members of the Ludlovian genus Lobograptus Urbanek. The significance of the thecal structure is discussed with reference to the principles involved in the classification of the monograptids.

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