In his “Palæozoic Fossils” (1861–65), Mr. Billings described, without figures, a fossil from the Black River Limestone, to which he gave the name of Stromatopora compacta. The description given was as follows:—“This species forms small subglobular masses, from one to two inches in diameter. The concentric lamellæ are thin and closely packed together, there being in some specimens from six to twelve layers in the space of two lines” (op. cit. p. 55).