296 DESCRIPTION OF CHALK CORALS. 
The fossil represented by figure 1, Tab. XVIII. B., occurred abundantly on a 
Micraster found by Lord Northampton in the Houghton chalk-pit ; likewise on 
the Ananchytes which gave the examples of Marginaria Roemeri. To the extent 
examined, no differences were detected from M. Michelin’s delineations of Diast. 
ramosa. One of the localities mentioned by that authority is Ciply, the strata 
in the neighbourhood of which have been placed by Dr. Fitton’ on a level with 
the Maestricht deposit or uppermost portion of the chalk ; and it is deserving 
of notice that other corals described in preceding pages have equivalents in St. 
Peter’s Mount. M. Michelin’s other locality is the vicinity of Mans, the bed 
from which his specimens were obtained being referred to the greensand. 
Assuming therefore that the corals are all rightly determined and geologically 
assigned, it follows that Diast. ramosa ranges nearly throughout the cretaceous 
series. Prof. Goldfuss’, under the term Cellepora echinata (Munster), has figured 
an Astrupp tertiary fossil, which resembles externally both the French and 
English corals, and should not possibly be generically separated from them ; but 
the assignment to Cellepora is evidently incorrect. 
The branched mode of growth of the three fossils agrees more nearly with that 
of Criserpia® than with typical species of Diastopora ; but in that genus additional 
tubes are wholly developed from the lower extremity and inner side of the pre- 
ceding ; whereas in the English chalk zoophyte and most probably in the French, 
they issue partly from the extremity of the parent tube and partly from the side‘, 
and without limitation to an inner position. Another distinction from the 
typical species (Cris. Michelint) is in the form and position of the mouth, which 
is not a simple tubular extremity, but a raised or outwardly inclined aperture 
developed at a definite period. In these particulars as well as in the characters 
of the tubes, no difference from Diastopora was detected; and if a branched 
mode of growth should be regarded as a generic distinction, it would be neces- 
sary to separate Tubulipora fimbriata® from its received genus ; also all corals 
generically in which a ramose or an expanded plan of production has hitherto 
been regarded only among specific distinctions. On the same Micraster, and 
intermingled with the fossil under consideration, was a species of Alecto, and the 
two Bryozoa were occasionally so intermingled that care was requisite to prevent 
* Proceedings Geol. Soc. Lond. vol. i. p. 162, 1829. * Petref. p. 102. tab. 36. fig. 14, 1826-1833. 
* Milne-Edwards, Ann. Se. Nat., Znde Série, Zool. tome ix. Mém. sur les Crisies, p. 16. pl. 16. fig. 4. 
* Consult M. Edwards's fig. 1 a of Diast. Eudesiana, op. cit. pl. 14. 
* Ann. Se. Nat. 2nde Série, Zool. tome viii. pl. 14. figs. 2, 2 a. 
