III.—Some new Rock-building Organisms from the Lower Carboniferous Beds of Westmorland

In my account of the Lower Carboniferous rocks of the North-West of England, published in 1912, I figured an organism, probably the thallus of a calcareous alga, which plays an important part as a rock-builder at the base of the Seminula gregaria sub-zone in Westmorland and Lancashire. More recently, at the meeting of the British Association in Birmingham, I pointed out the need of some distinctive name for this important form, and suggested for it the generic name of ‘Ortonella’, from the village of Orton, near Tebay, in the neighbourhood of which this fossil is specially abundant. Two other structures were mentioned at the same time which occur constantly in microscopic sections of the Lower Carboniferous rocks of the North-West of England and elsewhere. The first of these was alluded to under the general descriptive term ‘festoon structure’, and the other was referred to Gurich's somewhat obscure genus Spongiottroma. In view of the zonal value of these organisms in the North-Western Province and the probability that they will be found to be widely distributed in the Lower Carboniferous rocks elsewhere, I propose here to give a somewhat fuller description of these forms than could be attempted in the limits of a presidential address.