Some years since Professor E. J. Garwood sent to me for examination some pieces of limestone from the Lower Carboniferous rocks in the Shap and Ravenstonedale districts of Westmorland, in which he had observed the rounded outlines of fossils with a structure which appeared to him to resemble that of Stromatopora. The rock in which the fossils were embedded was so compact and hard that they could not be extracted, and it was necessary to make sections in various directions in order to ascertain their structure, which proved to be identical with that of Solenopora, now well known as one of the calcareous Algæ. It is many years ago since this genus was recognized in the Ordovician rocks in North America, Britain, and Eussia; more recently it was found in the Silurian rocks of the Isle of Gotland, and in 1894 a species was described from the Jurassic rocks of Gloucestershire and Yorkshire. But until this fortunate discovery of its occurrence in the Lower Carboniferous by Professor Garwood, no example of the genus was known in any of the rocks between the Silurian and the Jurassic.