DESCRIPTION OF CORALS. 139 
moreover be removed from Ehrenberg’s family Dedalina, characterized by the 
subdivisional process, to that of Ocellina, in which reproduction is effected by 
germs or developments in the mantle (op. cit.). 
Among the tertiary fossils assigned by M. de Blainville to Siderastrea, the 
only species which bears an approximate resemblance to the Bracklesham coral 
is the Astrea crenulata of Goldfuss as represented by M. Michelin*, but the 
stars of that polypidom are stated to be separated by a groovef, a structure 
which does not occur in the English coral at any period of growth ; and accord- 
ing to Prof. Goldfuss’s delineation of the same species, from apparently an aged 
or fully developed Piacenza specimen}, the two polypidoms differ essentially, at 
that stage, in the nature of the lamella and in the mode of union of adjacent 
stars. Among the other Paris basin corals described and figured by M. Michelin, 
Astrea Ameliana of De France$ (Ast. muricata, Goldfuss||) and Ast. hirtolamellata 
(Michelin§]) resemble generally the fossil under consideration, particularly in its 
earlier states of growth. Ast. Ameliana, however, is described as having all the 
lamella equal, whereas in Siderastrea Websteri they are unequal and more or 
less grouped in specimens of apparently equivalent age with that figured by M. 
Michelin ; and M. de Blainville refers Ast. Ameliana or muricata to his subgenus 
Dipsastrea, an assemblage of very differently constructed anthozoa. With 
regard to Ast. hirtolamellata, the other assumed analogous coral, M. Michelin 
states that it is also a Dipsastrea**, and so far as the characters have been 
illustrated, there are no means of determining satisfactorily the process by which 
additional stars were produced. 
The fine series of Siderastrea Websteri submitted to examination included 
interesting examples of growth, and of the mode by which interpolated germs 
advanced towards maturity. The beautiful specimen represented in part by 
figure 5a. Tab. I., formed one of six groups of stars of unequal lateral and 
vertical dimensions. ‘The greatest diameter of the smallest group was only 3 
lines, but the patch was very nearly united to another by the extension of the 
base-lamina, and the larger assemblages afforded proofs of similar junctions. No 
case was noticed of an isolated, immature star, such as might have arisen from 
a single transported germ; but the small group above alluded to had most pro- 
* Teonographie, Paris Basin Series, p. 156. pl. 44. fig. 1. 
t Goldfuss, Petref. p. 71, and Michelin (eopied), p. 156. { Op. cit. pl. 24. fig. 6. 
§ Dict. Se. Nat. tome xlii. p. 384. || Op. ett. p. 71. pl. 24. fig. 3. 
q Iconog. p. 162. pl. 44. fig. 5. ** Teonog. loc. cit. 
