Many species of _Flustræ_ occur in the British strata: the encrusting forms are attached to echinites, shells, &c.; the foliaceous are imbedded in chalk, sand, sandstone, &c. In Mr. Morris's _Cat. Brit. Foss._ ten species are enumerated; none of these are from formations below the Chalk. I have selected for illustration a Flustra attached to an echinite from Lewes. _Lign. 89, fig. 5_, represents a small portion of the natural size; and _fig. 4_, a few cells magnified, to show their form and arrangement. A foliaceous zoophyte, apparently a bryozoon, is abundant in the Sussex and Kentish chalk, and is often disposed in angular folds. It is generally of a ferruginous colour, and, from its friable texture, it is probable the original consisted of a membranous polypidom or calcareous substance; specimens sometimes extend over several square inches of the chalk. It is common in the chalk-pit at Off ham, near Lewes.[251] [251] In my South Down Fossils, pl. xv. _fig._ 6, a specimen of this kind is described as a Ventriculite, _V. quadrangularis_. An admirable lignograph of a remarkable example is given by Mr. Toulmin Smith, under the name of _Brachiolites angularis_; it presents ten deep, flat, angular folds, and has radicle and lateral processes; see "On the Ventriculidæ," p. 93. Eschara.[252]--In these zoophytes the polyparium is encrusting or foliaceous, calcareous and brittle; the cells are thickened on their outer margins, and have a small, depressed, round aperture. They are arranged in two series of planes, adhering together, the cells on each surface exactly corresponding. [252] So named from a supposed resemblance to an eschar. Species of Escharæ are found either in flints, or attached to echinites, and other bodies; they have the appearance of patches of flustræ, but with a lens may be distinguished by the symmetrical juxtaposition of the cells on the opposite sides of the polyparium. [Illustration: _Ellen Maria Mantell, ad nat. delt._ Lign. 89. Corals from the Chalk and Mountain Limestone. Fig. 1.--Carophyllia centralis; _nat._ (G. A. M.) _Cret. Lewes._ 2.--Front view of half the disc of the same. 3.--Two cells of Crisia Johnstoniana. × ×. 4.--Magnified view of six cells of the Flustra, _fig._ 5. 5.--A portion of an encrusting Flustra; _nat._ _Cret. Chichester._ 6.--Idmonea (Dixoniana) cretacea; _nat._ _Cret. Lewes._ The figure on the left shows the under surface; that on the right, the upper surface, with a row of polype-cells on each margin: a portion magnified is given _fig._ 12. 7.--Millepora rhombifera. × ×. _Mt. L. Ph. Yorks._ The small figure on the left is of the natural size. 8.--Pustulopora pustulosa. × ×. _Cret. Chichester._ The small figure on the left, _nat._ 9.--Homœsolen ramulosus. × ×. _Cret. Dover._ The left-hand figure, _nat._