SUB-GENUS FERONOPOKA. 219 



b), the ordinary corallites are seen to be of two kinds, large and 

 small. The large corallites are irregularly oval or circular, 

 the irregularity of the outline of the visceral chamber being 

 due to the projection into it of from one to three " spiniform 

 tubes," which cause an inward deflection of the wall at the 

 point where they occur. Each large corallite, also, exhibits in 

 its interior a delicate horizontal calcareous lamina, which ex- 

 hibits a larger or smaller semicircular deficiency on one side. 

 This excentrically perforated lamina represents the singularly 

 incomplete vesicular tabulae of the large corallites, as seen 

 when transversely divided. Tangential sections, further, ex- 

 hibit a variable number of smaller corallites, which occupy the 

 intervals between the larger tubes, and are very variable in 

 shape and size, their numbers also varying in different parts of 

 the same specimen, or in different specimens, but which do not 

 show the incomplete tabulae of the large tubes. We can also 

 readily detect in such sections the stellate groups of small 

 corallites ; and these are seen to consist of a larger or smaller 

 collection of the interstitial corallites, with occasionally a few 

 of the large tubes intermingled with them. One of the most 

 conspicuous features in tangential sections, however, is the 

 presence of a great number of thick-walled, darkly-outlined 

 tubuli, of circular shape and very minute size, each present- 

 ing a definite central hollow or lumen, and often causing by 

 their presence an inw^ard projection of the walls of the large 

 corallites. 



These " spiniform corallites " vary in number in different 

 specimens, but they are always present ; and by microscopic 

 examination they can usually be readily detected at the surface, 

 appearing either as very minute, circular, thick-walled apertures, 

 or as blunt and rounded tubercles which show no apparent 

 opening. Lastly, tangential sections show that the walls of 

 the corallites in this region are apparently fused with one 

 another, no traces of the original lines of demarcation between 

 adjoining tubes being recognisable. 



Tangential sections taken at a rather deeper level below 



