A Graptolite Lineage from North Cardiganshire

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Abstract
As the result of examining a considerable number of specimens belonging to the species Monograptus fimbriatus, M. raitzhainiensis, and M. triangulatus from certain strata of Llandovery age at a locality in North Cardiganshire, the writer is led to the conclusion that the forms comprised within these species constitute a continuously graded morphological series; and that the stratigraphical occurrence of these forms shows that this series is, further, an evolutionary lineage.

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