The Silurian Species of Glauconome, and a Suggested Classification of the Palæozoic Polyzoa

Abstract

T he genus Glauconome , originally founded by Goldfuss, was so modified by Lonsdale, as to become virtually a new genus, of which Glauconome disticha from the Dudley Limestone is the type. Later on came the discovery by Sedgwick of apparently a similar polyzoan from the Bala beds of North Wales. This was regarded by Prof. McCoy as identical with the Wenlock species, and, as such, has been generally received. We have been of late examining these Silurian species of Glauconome , both as to their identity with one another and their connexion with the Carboniferous and Devonian species, and we find that the Bala and Wenlock species are not even generically related, while the members of the large Carboniferous group have not the least affinity with the type species from the Wenlock beds. The present Bala, Devonian, and Carboniferous species evidently belong to a modified group of the Cyclostomatous Polyzoa, while the type species from the Wenlock can only be classed in a distinct division of the Polyzoa, for which at present no provision is made. In coming to this decision, we have been mainly guided by zoarial form, and not outward resemblance. Evidence in this direction has been carefully sought for in the several species. In Glauconome disticha from the Wenlock Limestone we find the cell open and exposed throughout its entire length; this, we find, is not accidental, but characteristic. The cells are built up of a series of thick longitudinal walls running parallel with the branch, and divided at