82 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 14, 



it will be found that the resemblance is limited to additional cavities 

 being in each case interpolated, with an occasional union of lamellae 

 in their outward extension . The latter structure presents in the fossil 

 species, instead of thin plates, with a deep, open, intermediate net- 

 w'ork, broad, rounded ridges in close contact (Goldf. fig. 3 a) ; and 

 there is necessarily a total absence of intervening textures ; the area 

 of the abdominal cavity also, in place of being contracted by extensions 

 of numerous lamellae, is but slightly encroached upon, and the bottom 

 of the cavity has apparently a uniform composition. The comparison 

 cannot be extended. In these structures however, Sid. alveolata 

 agrees perfectly with the lower greensand fossil, and the latter is 

 consequently to that extent equally distinct from Sid. yalaxea. If 

 the internal composition of the recent coral be considered wdth refer- 

 ence to that of the Atherfield zoophyte, great dissimilitudes will be 

 evident. The lamellae, instead of being thin throughout and appa- 

 rently simple, solid plates, are in the fossil, as already stated, broad 

 (fig. 12*), and are internally cellular, and necessarily without separated 

 sides beset w ith papillae : the abdominal cavity again, in lieu of being 

 progressively occupied by numerous vertical lamellae united in the 

 centre of the area into a solid axis, is penetrated to a limited extent 

 by only four attenuated lamellae-edges, and is successively crossed by 

 laminae of variable transverse range and curvature, without a trace of 

 an axis. These differences, it is conceived, fully justify the conclusion 

 that the fossil under examination is not a Siderastrcea, and it is be- 

 lieved that i\I. Goldfuss's coral possesses a similar generic composition. 



iii. It is not necessary to dwell even generally upon the established 

 recent and fossil groups, which resemble the lower greensand zoophyte 

 in being aggregated and many-lamellated ; also in having the abdo- 

 minal cavities crossed by laminae without a continuous vertical axis, 

 likewise in having additional stars developed in the interspaces ; as in 

 only one instance, the CyatJwphora of M. Michelin, is there such a 

 combination of structural agreements as to warrant a detailed com- 

 parison. 



M. jMichelin states that Cyathopliora Richardi-^ consists of aggre- 

 gated polj^gonal tubes divided by diaphragms ; the stars deep, subpo- 

 lygonal, radiated to a small distance, and the margin thick. He adds, 

 that the lateral lamellae are little visible, though numerous, resembling 

 striae ; and that the plates in the terminal star cover scarcely half the 

 surface of the last transverse lamina. His figure 1 a represents a 

 considerable diversity of range, inclination and curvature in the plates 

 which cross the cavities ; but neither the description nor the illustra- 

 tions afford any information respecting the composition of the lamellae, 

 or of the spaces between the abdominal receptacles ; there is also no 

 allusion either in the generic or specific notice to the mode of deve- 

 loping young "tubes," but the small, round depression in figure 1 b 

 indicates an interpolated origin. 



In attempting to compare these characters with the structures of 

 the lower greensand fossil, it must be mentioned that weather-worn 



t Iconographie Zoopliytologique, p. 104, pi. 24. fig. \a,\b, 1844? 



