In the Comatulidæ, the arms are distinct from the body; these animals therefore closely approach the Crinoideans: in the true Star-fish, the angular processes, or arms, are an integral part of the body, containing a portion of the stomach, ova, &c., and are furnished with rows of pseudopodia. Fossil Comatulæ have been discovered in the Solenhofen slate; and it is not improbable that some of the numerous Crinoideans may be Asteriadæ in the early stages of development. In another group, Asteriadæ, (named _Ophiuræ_ or Serpent-stars,) the rays are long and slender, and without grooves or tentacula, and are distinct from the body. These organs are extremely flexuous, and in some species beset with spines, and enable the animal to seize and entwine round its prey. The mouth is central, and there is an ovarian aperture at the base of each of the five arms. Though the fossil Star-fishes comprise many extinct genera, they belong to the same families as the recent; and Comatulæ, Ophiuræ, and Asteriadæ, occur in the Lias, Oolite, and Chalk, in considerable numbers. Professor Edward Forbes has determined many of the British species, and it is to be hoped, will publish a monograph on the Fossil Asteriadæ, as a companion to his delightful work on the recent Star-fishes. [Sidenote: FOSSIL OSSICULA OF STAR-FISHES.] Fossil Ossicula of Star-fishes.--From the immense number of little bones which enter into the composition of the skeleton of a single Star-fish, and which are but slightly held together after the death of the animal and the decomposition of the soft parts, we can understand how layer upon layer of ossicula of Asteriadæ may have been formed at the bottom of the cretaceous seas; as we find them in the quarries near Arundel, Worthing, &c. Whoever has witnessed the hauling up of the dredge off our coasts, and seen the mass of living Star-fishes which it brings up, as if the sea-bottom were a living bank of these Radiata, will not be surprised at the vast quantities of their fossil remains. This profusion of the living animals of this family, serves also to account for the enormous amount of those kindred but extinct forms, whose relics were the subject of investigation in the former part of the present chapter.