On the Discovery of Melonites in Britain

Abstract

I n the appendix to a paper read before the Geological Society, June 9, 1875, I noticed the discovery of a large Urchin, nearly allied to the American genus Melonites , from the Carboniferous Limestone of Derbyshire, and preserved in the museum of the Geological Survey. I have since been permitted to examine the specimen more carefully, so as to determine it to be a new species of Melonites, a type of Echinoids characterized by its numerous ranges of ambulacral plates, which until now was unknown beyond the boundaries of the New World. Another fragment, smaller, but well preserved and presenting all the characteristics of the species, may be seen in the British Museum. Description of the specimens .—The larger specimen is a confused mass of stout plates covering an area of seven and one-half inches by 7 inches. Among these may be seen some broad bands and broken masses of another set of plates, which are each perforated by a pair of pores. From the arrangement of this latter system of plates, converging, as they do, rougMy to the centre of the specimen, we see that this is the remains of one large Echinoid broken up and much disarranged, the larger scattered plates having formed its interambulacral areas, the masses of smaller plates its ambulaeral zones. The interambulacral plates (figs. 3, 4) are very numerous, and are all about the same size, which shows that new series of plates were intercalated to form the increasing circumference towards the equator of the test, where there