Page:Quarterly Journal of the Geological Society of London, vol. 29.djvu/486

 spinules of the first-mentioned structures often give them a pinnate appearance. Granulation and radiating lines mark the upper part of the capitulum ; and these last are especially well seen when the crateriform projection resembling an oral orifice is visible.

The only perforations of the calcareous investment are at the distal end of each tentacular process, and on the upper surface of the capitulum. The general surface is not perforate. There are, however, in a few specimens some few irregular-shaped openings on the underside of one or two tentacular processes ; and a few stems present indications of an opening close to the capitulum. It is evident after careful examination that the openings in the distal end of the tentacular processes are normal ; and they may have permitted the internal structures to communicate with the outside medium ; but the inferior openings are either the result of compression, or of the dislocation of ornamentation. The capitular opening, with its radiating lines and projecting eminence surrounded by the tentacular processes, is a part of the structural ceconomy of the form ; and even when the upper capitular surface is flat it may be discovered by gentle scraping. It would appear that several flap-like processes enter into the composition of the prominence which ends in the opening, after the fashion of a metastome. The openings in the stems are to be referred to the fracture of a calcareous and hollow process — which is to be seen intact in a few specimens, and broken across at a short distance in others. The tentacular processes vary in length and in number. The extreme length may be half an inch ; and the position of many of them indicates that they were not absolutely rigid. Some are long and others are short in the same whorl ; and one specimen may have seven, whilst others may present four, five, eight, or more tentacles. Usually one process is larger than the others, and not symmetrically placed.

There are no cellular dissepiments within the cavities of the capitulum and stem ; and the calcareous investment of these structures is thin, readily scraped, and in no way resembles the calcite of the Echinodermata.

In the communication to the Royal Society, my colleague and I represented the form, which clearly could not belong to the Echinodermata, Zoantharia, or Polyzoa, to be one of the Hydroida, having affinities with the recent Bimeria vestita (S. Wright).

In this genus there is a chitinous coat, by which sand grains and spicules are mechanically suspended, covering the base, stem, and body and tentacles, leaving an opening for the metastome and for the distal end of the tentacles.

We considered the fossils to be the trophosomes of a hydroid, and that the process beneath the capitulum on the stem might be the gonosome.

The crateriform aperture we believed to be the mouth : and we assumed that the opening at the distal end of the tentacular processes gave exit to a ciliated tentacle during life.

Parasitic (or, rather, placed) upon a Fenestdla, the form would