80 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jlllie 14, 



that coral the fissiparous process passes through the reticulation, 

 sometimes producing a perfect hipartition. The characters of the 

 abdominal cavity are also diiferent, and the lineal extension of the 

 central network is so much greater, that it would be almost impos- 

 sible to form a new receptacle for viscera within a previous area 

 without including a portion of the reticulation. There is a farther 

 very marked structural distinction in the stars being separated by 

 broad intervals, one of the characters on which Ehrenberg founded 

 his generic separation, Favia. The existence of those spaces might 

 lead to the supposition that young stars would be developed among 

 them. Their existence however was clearly necessary for the pecu- 

 liar construction of the animal; and in neither Esper's figures {op. cit. 

 pi. 71), nor in a specimen of similar dimensions, was the upwards 

 growth sufficient to occasion a considerable radiation ; while the pro- 

 gressive thickening of the intervals between divided cavities seemed 

 fully to meet the effects of divergence and prevent an excessive di- 

 stance between the stars : moreover, not a sign of a young interpola- 

 tion could be discovered. This inquiry must not be continued far- 

 ther ; but in the two cases quoted, considerable differences are shown 

 to attend the fissiparous process, accompanied by marked structural 

 variations, and they are sufficient to induce caution in studying 

 organic remains. Among fossil corals other perfectly distinct modes 

 occur of developing additional cavities within the pre-existing ; and 

 the author of this notice erred, when in 1839 he retained, even pro- 

 visionally, the term Ast. ananas for a Silurian fossil*. With re- 

 spect to the Atherfield zoophyte, not a vestige of a subdivision was 

 discovered in the many specimens submitted to examination by 

 Dr. Fitton. 



ii. ]\I. de Blainville having removed Ast. aheolata to Siderastrcea 

 {ante, p. 77), the composition of that subgenus must now be noticed, 

 as well as the amount of agreement with M. Goldfuss's species and 

 the lower greensand fossil. Prof. Edwards considers the group as 

 possessing marked characters (Lamk. p. 404). It comprised origi- 

 nally three recent and twenty-eight fossil species ; but respecting the 

 former some diversity of opinion will be found in the following equi- 

 valents : — 



1. //5#.AS'z(Z6'ra5/r«as?<7^refl,DeBl.p.370=Paz?om'az<?.,Dana,Expl.Exp.p.331,1846. 



2. — galaxea, ,, ,, =Siderina id., ,, „ ,, p. 218. 



3. — cactus, „ „ = Pavonia id., Ehrenh.fBe'itrage, ]). 105. 



Respecting the first species as originally described in Ellis and So- 

 lander little is knownf, and ^Ir. Dana {loc. cit.) doubts the correct- 

 ness of Lesueur's identification with it of a West Indian coral :]:. The 

 animal of the latter is moreover stated to be tentaculated, and that of 

 Ast. galaxea to be non-tentaculated (Lesueur, oj). cit. p. 285). Under 

 these circumstances it would be unadvisable to adopt Ast. siderea as 



* See Sir R. I. Murchison's work on the Silurian System, p. 688, pi, 16. fig. 6. 

 f Consult the figure, pi. 49. fig. 2, of Ellis and SoL, or Laraouroux, Expos. 

 Method. 



X Mem. du Museum, t. vi. p. 286, pi. 16. fig. 14. 



