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.
Beautiful Cidarites and their spines may be collected in the Oolitic strata at Calne, Chippenham, Bath, &c.; and in the coralline Oolite near Faringdon; and of Saleniæ, in the Greensand gravel-pits near that town.
The Upper Greensand near Warminster, and at Chute Farm, near Heytesbury, abounds in small Cidaritidæ and other echinites. The large sinuated Clypeus is found in great perfection in the Oolite at Malton, Cheltenham, Gloucester, &c.
The cretaceous echinites are to be met with in most localities of the white chalk. The chalk-pits in Kent, especially at Gravesend, Northfleet, Chatham, &c. are rich in Cidarites, and their spines. The Galerites, and Ananchytes, are also very fine and numerous; and the softness of the chalk renders their extrication from the stone a delightful task for the young geologist.
Specimens of the common kinds of fossil Echinoderms may be obtained at moderate prices of the dealers named in the Appendix.