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.
10.—Crisia (?) Johnstoniana. (G. A. M.) × 250 linear.
S. s. Maidstone.
10b.—Two cells of the coral, fig. 10, seen in profile, × ×.
11.—Homœsolen ramulosus; nat. Cret. Lewes.
12.—Idmonea Dixoniana; a portion of fig. 6. ×.
13.—Retepora laxa. Mt. L. Ph. Yorks.
13†.—A portion of the same ×.
14.—Idmonea Comptoniana. × ×. (G. A. M.) Chalk, Chichester. (Mr. Walter Mantell.)
The small figure on the right is of the natural size.

MICROSCOPIC FOSSIL BRYOZOA.

Crisia Johnstoniana. [Lign. 89, fig. 3, 10, 10b.]—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 very curious polypidom from the Greensand of Maidstone, presented to me by Mr. Bensted. 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. 10b the same seen in profile.[253] I have named this species C. Johnstoniana, as a tribute of respect to the author of the admirable works on British Zoophytes, previously noticed.

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

The fragmentary relics of numerous minute and elegant corals, constitute a considerable portion of the mass of some of the white chalk strata; several genera of these zoophytes are figured in Mr. Dixon's beautiful work, and described by Mr. Lonsdale. Attached to the surface of shells, &c., and sometimes standing erect in little crannies, or hollows, of the flints, many beautiful corals may often be detected with the aid of a lens. By brushing chalk in cold water, and examining the deposit, the student will probably discover several of the species figured in [Lign. 89], which we proceed to describe.

Retepora (Lace-Coral). [Lign. 89, fig. 13.]—A very thin calcareous polyparium, disposed like net-work in foliaceous and branching plates; cells opening either on the upper or inner side.

These are an elegant tribe of corals, of which many species occur in the Chalk formation at Maestricht, in the white-chalk of England, in the mountain limestone of Yorkshire, (Phil. York.), and in the Silurian deposits (Sil. Syst.). It may be useful to state, that in the description of the fossil retepores, the openings in the net-work are called fenestrules—the spaces between the ends, dissepiments—and those between the fenestrules, interstices. A delicate fossil retepore from the mountain limestone of Yorkshire (R. flexa), is figured [Lign. 89, fig. 13].