284 DESCRIPTION OF CHALK CORALS. 
In the observations, however, on the German specimens, the coral is considered 
the type of a peculiar genus. Both the foreign and the English fossil consist of 
slender, round, forked stems, traversed vertically by smooth, projecting, straight 
ribs, between which occur the apertures to the abdominal cavities ; also subordi- 
nate ribs of limited extent, and rows of minute pores. The branches are similarly 
occupied over the whole surface, except where irregularities occur or changes due 
to age. Herr Roemer says, his specimens formed cespitose groups on a knotty 
base ; and Mr. Dixon's bore full testimony to an aggregated mode of growth, 
though no base was observed. 
The chief point of agreement with Lamouroux’s' Chrysaora appears to consist 
in the lineal projections. How far ribs may be essential components of that genus 
remains to be ascertained; but judging from published delineations of Chrys. 
Damecornis*, they seem not to be persistent ; on the contrary, in the English 
chalk fossil, they clearly form a leading constituent throughout the framework. 
Such ridges moreover are not confined to Chrysaora. They occur very markedly 
in M. Milne-Edwards’s Hornera striata®, but if considered in conjunction with the 
other structures, no agreement whatever will be found between that fossil and 
Chrysaora Damecornis, or with the zoophyte under examination. Chrysaora, 
moreover, has no secondary openings, a prominent character in Herr Roemer’s 
species and in the English equivalent. Again, no changes dependent upon age 
have, as yet, been mentioned in the notices of the corals referred to Lamouroux’s 
genus ; whereas great alterations are very manifest in Mr. Dixon’s specimens of 
the chalk fossil; but admitting that they may exist, still, as in the latter instances 
they derived their peculiarities from those portions of the polype which formed 
the secondary pores and associated minor structures, and as no similar pores 
occur in Chrysaora, the changes would be very dissimilar, Heteropora* is the 
only other ascidian zoophyte known to the compiler of these memoranda which 
appears to require a remark. That genus has for a leading characteristic two 
sorts of pores distributed over the whole surface ; but in the representations of 
the typical species®, there is nothing to justify a belief of the fabric being simi- 
larly constructed to that of Herr Roemer and Mr. Dixon’s fossil ; and in the pub- 
1 Exp. Méthod. p. 83. tab. 81. f. 6-7 & f. 8-9. 
> [bid. tab. 81. f. 8-9; also Michelin, Iconographie Zoophytologique, pl. 55. f. 9 b. 
’ Mém. sur les Crisies, &c., Ann. Se. Nat. 2nde série, Zool. tome ix. pl. 11. f. 1 @; or Recherches 
sur les Polypes. * De Blainville, Man. d’Actinol. p. 417. 
° Goldfuss, as quoted by De Blainville, pl. 10. f. 3, 5 & 9. 
