316 DESCRIPTION OF CHALK CORALS. 
deeply downwards, the walls of adjacent cells being structurally united ; and 
where irregular interspaces occurred they were solidly filled up. The attempts 
to detect connecting foramina in the walls totally failed. The back lamina of 
the cell was very thin, the minute papillz of the Ananchytes rising through it. 
On the same Echinoderm occurred specimens of Flustra? inelegans and Es- 
charina ? intricata. 
Escharina ? intricata. (Tab. XVIII. B. figs. 8, 8a, 8b.) 
Incrusting ; cells arranged in alternate rows or irregularly, not successively 
overlaid ; form oval, boundary a furrow; perfect, surface convex, with a fora- 
men near the centre; mouth at the distal extremity, ovarian capsule a distinct 
chamber between successive cells. 
The genera with which this fossil presents points of agreement, are Marginaria 
of Herr Roemer}, and Escharina of M. Milne-Edwards?. The former is stated to 
consist of an incrusting layer, composed of cells with thick, distinct edges, sepa- 
rated by a furrow, the covering being flat and often quite wanting. Herr Roemer 
refers to his genus the Cellepora Velamen as well as C. bipunctata of M. Goldfuss? ; 
and Herr Geinitz4 the Cellep. elliptica of Von Hagenow. If the delineations of 
those zoophytes be compared with figure 8, illustrative of Mr. Dixon’s coral, 
an agreement will be found in the large open spaces, bold boundaries and sur- 
rounding furrows or interspaces ; and to that extent the English fossil accords also 
with the generic characters: but the figures of the foreign species can be only 
regarded as representing either immature states, or cells deprived of their external 
covering, whether calcareous or membranous ; and the open areas of Mr. Dixon’s 
coral, shown in figure 8 a, undoubtedly had been divested of a solid lamina. Im- 
perfect conditions also, from whatever cause they may arise, are not by them- 
selves grounds for generic determinations ; and without questioning the correct- 
ness of Herr Roemer or Herr Geinitz’s decision, no zoological identity ought to 
be established between the figures quoted or given by them and the English fossil. 
Moreover, a flat exterior is one of the characters of Marginmaria, and the enlarged 
representation of M. denticulata® has a level surface ; a projecting boundary wall 
in a mature state is another, the plate forming the exterior being situated below 
! Verst. Norddeutschen Kreidegeb. p. 12. tab. 5. f. 3. * Lamarck, ed. 1836, t. ii. pp. 217, 230. 
5 Petrefacten, p. 26. tab. 9. f. 4. and p. 27. tab. 9. f..7. Locality for both species Maestricht. 
* Charak. Petref. siichsisch-bohmischen Kreidegeb. p. 93. tab. 22. f. 16 a, B. 
* Roemer, op. cit. tab. 5. f. 3. 
