TAB. XVIII. 

 CORALS FROM THE CORAL RAG. 

 ISASTREA EXPLANATA (p. 94). 



Fig. 1. Side view of a specimen, in which the epitheca has been partly removed in 

 order to show the mode of arrangement of the costse ; natural size. 



1 a. Calicular surface of the same ; natural size. 



1 h. Calice, magnified. 



1 c. Horizontal section, magnified. 



1 d. Specimen, in which the calicular fossula has been filled up by a calcareous 



deposit that assumes the appearance of a tuberculose columella. 



ISASTREA GrEENHOUGHI (p. 96). 



Fig. 2. Portion of the calicular surface somewhat worn ; natural size. 



Thamnastrea concinna (p. 100). 



Fig. 3. Side view of a large specimen; natural size. 



3 a. A portion of the common basal plate, showing the wrinkled epitheca ; natural 



size. 

 3 h. Calices in a good state of preservation, magnified. 

 3 c. Calices much weather-worn, magnified. 



