4 HiCKSON, .VtTc' Oitoradiatc Coral, Pyyophyllia iiifiala. 



defined lari^er septum before it fuses with tlie others. In 

 the lower parts of the coralkim the arrangement is not 

 exactly like that shown in Fig. 3 throughout, but gaps 

 occur between protosepta and columella, bringing the 

 intcrseptal cavities into communication with one another. 

 The eight metasepta do not apparently fuse either with 

 the protosepta or with the columella. They can be traced 

 from the margin of the calyx to the upper part of the 

 inflated base. The arrangement of the septa in this 

 region has not yet been determined, but both septa and 

 thecal wall are here very much attenuated. The base is 

 not perforated, nor does it show any evidence of attach- 

 ment. 



Fig. 4. — Side view of llie coral Pyyopltyllia iiiJJata. sliowini; the 

 costae, the annular ridges, and the inflated base x 8 diameters. From 

 a photograph by Mr. Jackson of llie Manchester Museum. 



Of the external surface of the coral very little need be 

 said at present. There is no evidence of an epitheca — in 

 the sense this term was used by Dimcan — as distinct from 

 the theca. There are sixteen distinct costal ridges extend- 

 ing the whole length of the coral and there are 15-20 

 (according to the age of the coral) transverse annular ridges 

 marking successive growth periods. Wherever the 

 annular ridges meet the costae, the latter project as 



