ASTEOCCENIiE OF THE SUTTON STOKE. 105 



The costse are crowded, and those of one calice pass on to the wall 

 of the next corallite and inter digitate "with its costse. 



A most instructive, much worn specimen, which was an old 

 colony at the time of fossilization, is in the Museum, and in the 

 section which has been made, it shows a few corallites cut through 

 transversely. The lumen of one corallite is separated from that of 

 the next one by a distance equal in breadth to the diameter of 

 the lumen. The cause is thickening of the united walls. There 

 is no exothecal cellular growth between the corallites, and they are 

 united by their thickened walls. The width of the united walls of 

 neighbouring corallites is very considerable in a specimen in the 

 Bath Museum, on which a Cyatlioccenia and an Ostrea are seen. In 

 some places in the fossil the corallite-walls are thin, the spaces 

 occupied by the septa and columella are small, and the lumen is 

 often circular, especially when the walls are thick. 



It is to be noticed that the transverse section of the lumen of a 

 corallite is often circular ; but the old corallite is none the less poly- 

 gonal in transverse outline. It is evident that thickening of the 

 walls occurred only during the growth of the coral, but it is appa- 

 rently sometimes increased by the subsequent infilling of the outer 

 parts of the corallite-cavity during fossilization. 



The last specimen to be noticed in the Museum in Jermyn Street 

 has the calices smaller than in the type, and some of them are trian- 

 gular in outline, all the others being pentagonal, hexagonal, or 

 square with rounded angles. The distance of the calices varies, and 

 in some places the walls are thin and in others thick. The circular 

 lumen, when it occurs, is within a polygonal wall in section. The 

 costae are unusually long in some parts where the walls are thick. 



In all the forms the Astrocoenian type is maintained. 



AsTROC(ENiA. iNsioNis, uobis, oj). cit. p. 19, pi. ix. figs. 1 and 2. 



There is a specimen of this well-marked Astrocoenia in the Museum 

 of Practical Geology, and it presents the structural peculiarities 

 which are to be seen in the tyP®? which is in the Bath Museum. 

 The calices are close in places and wide apart in others, and in the 

 first instances they are pentagonal in outline, while in the others 

 they have a circular lumen, and this is within the polygonal waUs of 

 the corallite. The position of the junction of the corallite-walls at 

 the surface is clearly indicated, but there is no structure between 

 them. 



The width of the united walls gave a very decided aspect to the 

 type, especially as the costa) were stout at the end and were on 

 the free surface. This is seen in the specimen now under con- 

 sideration, and yet the opposite condition is noticed in parts. 



ASTEOCCENIA. PARASITICA, Uobis, OJ). Clt. p. 20, pi. V. figS. 5, 6. 



The type of this species is in the Museum of Practical Geology, 

 and it has been carefully reexamined. The coral encrusts foreign 

 bodies, and, in the instance of the type, a Palaeozoic coral is the 



