On a Siliceous Zoophyte, Alcyonites Parasiticum

Abstract

Parkinson in his ‘Outlines of Oryctology’ has applied the term Alcyonites to designate those fossils which were supposed to have been polypiferous animals allied to the recent genus Alcyonium . I have therefore adopted that name as being the best designation of the fosssil I am about to describe, although there is an objection to the term from the very indefinite and promiscuous manner in which it has been formerly used by authors; and Mr. Morris, possibly for the same reason, has judiciously excluded it from his ‘List of British Fossils.’ However that may be, in the present case it is applied strictly in accordance with the correct definition of the recent genus Alcyonium given by Dr. Johnston in the second edition of his excellent and beautiful ‘History of British Zoophytes.’ The fossil which forms the subject of this memoir is not in its natural and unmutilated condition, but is a portion of the animal contained in a small slab of agate 1 1/2 inch long by 1 1/18 inch wide, such as are commonly mounted in ladies' brooches. I obtained it from a dealer along with a considerable number of specimens of what are generally designated as Moss Agates. It is represented of the natural size, Plate VIII. fig. 1, and a fibre magnified 100 diameters by fig. 2. Alcyonites parasiticum. Polypidom fleshy, parasitic, incrusting, mammillated. Cells numberous, protuberant, scattered. Polyp. Tentacula short, cylindrical, smooth, tapering to an obscure point. At the first view of