In Mr. Morris's cata

chalk, sand, sandstone, &c. logue of British fossils, ten species are enumerated, but none are named from formations below the Cretaceous. A foliaceous Flustra is abundant in the Sussex and Kentish chalk, and often appears in flexuous folds, assuming a quadrangular form.* This species is generally of a ferruginous colour, and from its texture being that of the chalk, the original may be presumed to have consisted of a horny or membranaceous substance. Specimens sometimes cover several square inches of the chalk. It is common in the chalk-pit at Offham, near Lewes. I have selected for illustration a Flustra attached to an echinite from the chalk. Lign. 64, fig. 5, represents a patch of this zoophyte of the natural size; and fig. 4, a minute portion magnified, to show the form and arrangement of the cells.

ESCHARA.†-Ly. I. p. 391. Polyparium encrusting, foliaceous, calcareous, brittle; cells thickened on their outer surface, with a small, depressed, round orifice.

Species of this zoophyte are found in flints, or attached to echinites, and other bodies. They have the appearance of patches of Flustræ, but, with a lens, the latter may be distinguished from them by the regularity and juxtaposition of their cells.

* In my South Down Fossils, Plate XV. fig. 6, a specimen of this kind is described as a Ventriculite.

† Eschara, from the supposed resemblance to an eschar.

Fig. 106. Two cells of fig. 10, seen in profile. xx.

11.-RETEPORA FLEXUOSA: nat. Cret. Lewes.
12.-IDMONEA DIXONIANA; a portion of fig. 6. X,
13.-RETEPORA LAXA. Mt. L. Ph. Yorks.

13*.-A portion of the same x.

14.-IDMONEA COMPTONIANA. xx. (G. A. M.) Chalk, Chichester, (Mr. Walter Mantell.)

The small figure on the right is of the natural size,

CRISIA (separated cells). Lign. 64, figs. 3, 10.— The minute recent corals thus designated are allied to Flustra, but separated from that genus by the cells being disposed in a single series, and united by connecting tubes. I notice this genus to direct attention to a curious polypidom from the Shanklin sand (Lign. 64, figs. 3 and 10.). The specimen is attached to a fragment of shell. The cells, five of which are represented, fig. 10, are elliptical, with the aperture above, and towards one extremity, They are united by very slender, hollow filaments. Fig. 3, two of the cells seen from above × 250 linear; fig. 10. the same seen in profile.* I have named this species C. Johnstoniana, as a tribute of respect to the author of the works on British Zoophytes, previously recommended to the student.

The detritus of numerous minute and elegant calcareous polyparia, constitutes a considerable portion of the mass of some of the cretaceous beds,

* I refer this fossil to the genus Crisia, with some hesitation; perhaps Hippothoea would be more correct, but all the described species of the latter are branched.

Attached to the surface of shells, &c., and sometimes standing erect in little crannies, or hollows, of the flints, many beautiful species may often be detected with the aid of a lens. By brushing chalk in cold water, and examining the deposit, in the manner previously recommended, the student will be able to obtain many of the species figured in Lign. 64.

Fossil species of the flexible zoophyte, Gorgonia, or Venus's Fan, are occasionally met with, and very fine specimens may be obtained from the loosely aggregated sandstone of Maestricht. (Wond. p. 307, Tab. 50.)

RETEPORA (porous net-work).—Polyparium stony, disposed in meshes; foliaceous, or branching; cells opening only on the upper or inner side.

These are elegant corals; several fossil species are figured and described, from the Chalk formation of Maestricht, the mountain limestone of Yorkshire, (Phil. York.), and the Silurian deposits (Murch. Sil. Syst.). It may be useful to state, that in the description of these fossils, the openings in the net-work are called fenestrules-the spaces between the ends, dissepiments, and those between the fenestrules, interstices.

Three minute species of this genus from the chalk are represented Lign. 64, figs. 8 and 11, and Lign. 54, fig. 1; and a very delicate Retepora from

the mountain limestone of Yorkshire (R. flexa), Lign. 64, fig. 13.

FENESTELLA.-Cells very small, indistinct externally, with small prominent openings; polyparium stony, fixed at the base, composed of branches, which inosculate by growth, and form a cup. (Murch. Sil. Syst. p. 677.). Numerous delicate corals, formerly arranged as Retepora, have, with much propriety, been placed in this genus by Mr. Lonsdale ; and the student, in examining slabs of the Dudley or Wenlock limestone, should remember the distinction.

MILLEPORA.-Pores very minute, perpendicular to the surface, giving the interior a finely striated fracture; form irregular.

There are many fossil species of this genus, some of which are branching, and of considerable size. Two small species are figured, Lign. 64; one from the chalk, fig. 9, and another from the mountain limestone, fig. 7. Considerable masses of a polymorphous milleporite, presenting a dense structure, are found in the chalk of Sussex and Wiltshire.

IDMONEA, Lign. 64, figs. 6, 14. - Polyparium stony, branched, porous, cells distinct, prominent, arranged in single rows on the inner face only.

A very beautiful coral, figured nat. size, Lign. 64, fig. 6, is found in the chalk of Kent and Sussex; it