FOSSIL ACTINOZOA. 



secreted by the coenosarc (fig. 40). The entire compound 

 corallum consists, therefore, of a greater or less number of 



Fig. Tfr.Petraia calicula. 

 Lower Silurian. 



Fig. 



aphrentis Stokesi. 



39. apren 

 Lower Siluri 



" corallites " bound together by a calcareous basis, which is 

 secreted by the coenosarc, and is called the " coenenchyma." 



Fig. 40. Synhelia Sharpeana. 



Iii practice, however, this theoretical view of the subject is not 

 always borne out. The compound corallum may. and often 

 does, consist (as in fig. 41) of a number of corallites produced 



