[1] The name was introduced by J. Phillips on account of the typical development of the phase in Yoredale (now generally known as Wensleydale), Yorkshire.
These limestone beds have received various names of local significance (Hardraw Scar, Simonstone, Middle, Underset, Main and many others), and owing to the country being little disturbed by faulting and being much cut up by the streams, they stand out as escarpments on either side of the valleys.
Posidonomya Becheri occurs fairly low down in the series in the Shale above the Hardraw Scar and Gayle limestones, but it is not accompanied by any of the goniatites or other cephalopods and lamellibranchs which characterize the Posidonomya Becheri beds of the Pendleside Series, the faunas of the Yoredale and Pendleside phases being very distinct.
The shales between the limestones are rich in fossils and contain abundant single corals referable to Zaphrentis enniskilleni, Cyclophyllum pachyendothecum, and others; these, though high-zonal forms, occur low down in the Yoredale strata, even in the shale above the Hardraw Scar limestone.
[4] Attempts have been made to correlate rocks in a number of widely separated areas with the Yoredale strata, but on wholly insufficient grounds.