Notes on Species of Phyllopora and Thamniscus from the Lower Silurian Rocks near Welshpool, Wales

Abstract

Mr. G. W. Shrubsole, in a paper “On the Occurrence of a new Species of Phyllopora in the Permian Limestone”, remarks that “the genus Phyllopora has as yet been but imperfectly worked; its rarity in the more recent and its imperfect preservation in the older rocks go far to account for this..... In the Lower Silurian rocks Phyllopora is most abundant. There are at least two distinct species, if not more. The preservation of the remains in these beds is most unfavourable for exact work, occurring, as they often do, in coarse ash or shale, and distorted by cleavage.” In the collection of the School of Mines there were several specimens of Phyllopora catalogued and labelled as such, which I was allowed to examine when collecting material for my Second British Association Report on Fossil Polyzoa. The specimens from the Lower Llandeilo rocks are the common forms, generally designated Retepora by early authors. One specimen is in the Wyatt-Edgell collection, and we have only the reverse aspect of the form; but in places where the branches are worn the cells can be seen, not sufficiently, however, to enable us to make out their character. The fenestræ are oval or irregular, branches anastomosing, consequently without dissepiments. In the Caradoc series of fossils of the same collection, several specimens are labelled, and also catalogued, as Phyllopora Hisingeri , M'Coy, and one, belonging to the Wyatt-Edgell collection, is catalogued as P. ornata , MS. Generally speaking, all these forms are very indistinct or ill-preserved. In