ALCYONIDA, a family of the Asteroid Polypes, containing the genera Alcycm.ium and Sarcodictyon. They are distinguished from the Pennatuliche (Sea-Pens), and the Gorgortiader (Sea-Fans), by the polype mass being tough and fleshy, without any distinct axis, but strengthened by the irregular distribution of calcareous spiculre. The polype-cells are placed hi the fleshy mass, and scattered over its surface. The best known of the species of this family is the Alcyoniunt digitatunt, which was described by Ellis under its popular name of Dead Man's Hand, or Dead Man's Fingers. It has been described by naturalists by other names, especially Lob ularia ; but this is inadmissible, as having beenpreviously employed to name a plant. A lcyonienn in derived front Alcyom the kingfisher ; and this word means sea-foarn, of which the kingfishers were supposed to make their nests The species in question is one of the most common of our mar:thee productions, and is found on stones and shells and rocke, and can frequently be collected at the low-water mark during a spring-tide. It sometimes covers the object to which it is attached as a mere crust, at other times it rises up in one or more conical masses. Where there is only one, the fishermen give it the name of the Cow's Papa, from its resemblance to the teat of the cow's udder. The akin is tough, and when examined presents little radiated points, which indicate where the tentacles of the polypes exist. The tentacles are short, obtuse, and
ciliated on the margins. The poly-pe-colls are placed just under the skin, at the termination of a series of aquiferous canals which run throughout the polype-nues. These tubes communicate with each other, so that many of the points are, as it were, collected together, forming a compound animal. The space between the tubes in occupied by a loots fibrous network, forming lozenge-shaped compartments, with smaller meshed in them. These interstices are filled with gela tinous matter, in which irregular calcareous epicuke lie embedded. The ova are developed in the polvpe-tubes, and aro about the size of a grain of sand. They are proauced in spring and summer, and ultimately discharged from the mouth of the polype.
A second species of Aleyonists, A. glomeruturs, has been described by Dr. A. H. Hassan.
The genus Sarcodictyon has been described by Professor Edward Forbes. It differs from Alcyonium in the incrusting, creeping, and anastomosing form it assumes. Its polypes also are distant from each I other, and placed in uniserial prominent cell& It has eight pinunted tentacula. Only one species has been described, S. catenate.
(Johnston, British Zoophytes.)