The _Asteridæ_ are so simple in form and structure, that it is unnecessary to offer any suggestions for their development; of course they must not be removed from the stone. Among the detached ossicula dispersed through the chalk, the student will remember that the large _madrepore-like_ tubercle of the Star-fishes, (_ante_, p. 304,) may often occur. It may easily be mistaken for an encrinital body, or for a coral, but an accurate inspection will show that it is not composed of anchylosed plates, like the receptacle of an Apiocrinite, but has surfaces for attachment to other ossicula; while the ends, which in a crinoideal column would have radiated surfaces, are rounded and entire. In collecting Echinites, much caution is required in dissecting specimens surrounded by spines. If imbedded in hard limestone, or in laminated clay, it is scarcely possible to preserve the spines in connexion with the shell; but it often happens that the Cidarites of the Oolite are attached by the base to the solid limestone, and the case with the spines is imbedded in sandy, friable aggregate, not difficult of removal. A specimen in my cabinet, with upwards of fifty spines attached to the shell, was obtained under such circumstances.[304] [304] Now in the British Museum. The Chalk Echinites will be found to possess spines more frequently than is commonly supposed, if care be taken to explore the surrounding chalk before it be removed. T have often procured Cidarites with spines, when there were no apparent vestiges of these appendages, by carefully scraping away the surrounding mass until the extremity of a spine appeared, and then tracing it up to its connexion with the shell; another point was discovered by further removal, and that was developed in the same manner; and at length a Cidaris with several spines was obtained. The chalk around the mouth should always be cautiously removed in the dentated species, in the hope of preserving the teeth, as in the specimens, _Lign. 101, fig. 1_, and _Lign. 104, fig. 1_. As the shells of Chalk Echinites, when hollow, are often lined with crystals (see _Lign. 103, fig. 3_), it is worth while to break all indifferent specimens of the common species, with the chance of obtaining an example of this kind. The chalk must not be _scraped off_ from the crust or shell of the Echinites, or the minute granulations and papillæ will be injured or removed; it should be flaked off with a blunt point. In friable arenaceous strata, as in some of the Maestricht and Tertiary deposits, the Echinites may be extricated in as perfect a condition as if fresh from the sea; it is, indeed, probable, from the habit of these animals of burrowing in mud and sand, that in many instances they were entombed alive by the sediment in which their fossil remains are imbedded.