The _Ophiocoma rosula_, figured on Plate 9, will serve to convey to the reader a general idea of this class of animals. Its popular title is the Common Brittle-star, indicative of the inherent fragility of the species, as also of their prevalent appearance at the sea-shore; but, though so exceedingly 'common,' we must at the same time in justice add, that the _O. rosula_ exceeds in beauty many other species which are rare, and consequently more highly prized by the collector. It is very abundant on all parts of the British coast, and is often found in clusters upon the stems of _L. digitata_, and as frequently upon the under side of boulders. In dredging, the Brittle-star is an unfailing prize. It is a marvellous sight when the scrapings of the ocean bed are spread out upon the dredging-board for examination, to see hundreds of these singularly delicate creatures twisting and twining about in all directions,--over each other's bodies, through the weed, sand, shells, and mud, and strewing fragments of their snake-like arms upon every surrounding object. At the mere mention of 'Star-fishes,' the most uninitiated reader will at once realize in his mind's eye a tolerably correct notion of the form of these curious productions of the marine animal kingdom, even although he had never seen a living or dead specimen. The body of the animal is divided into rays, like the pictured form of one of the heavenly stars, and the fancied resemblance is most apparent in the Asteridæ, or true Star-fishes, of which we are now about to speak. This wonderful race of animals, for their beauty of colour, elegance of shape, and peculiarity of structure, possess a great degree of interest, not only to the naturalist, but also to the casual observer by the sea-side. There are fourteen British species of Asteriadæ, which are arranged under four families, namely--the Urasteriæ, the Solasteriæ, the Gonasteriæ, and the Asteriæ. This group contains no less than eight generic types, clearly distinguished from each other by certain characters, 'derived from the outline of the body, the number of rows of suckers in the avenues, and the structure and arrangement of the spines covering the surface and bordering the avenues.' There are four species of Star-fishes belonging to the genus Uraster, the most common of which is the _Uraster rubens_, or Common Cross-fish. No person in the habit of visiting the sea-shore can be unfamiliar with the likeness of this creature, which is generally seen lying wedged in some rocky crevice, or among the Fuci, there patiently waiting the return of the tide. At such a time, the Devil's-hand (as the Irish people term it), does not appear by any means attractive. If placed in water, however, its appearance becomes wonderfully improved.