Morphology of the Madreporaria. 



233 



rarely, however, tluit one secures examples of these ancient 

 corals having perfect tips, and otherwise of such a character 

 that the arrangement of the earliest septa can be made out, 

 either from microscopic sections or grinding down. Speci- 

 mens of Lopliophyllum proUferum^ the species first studied in 

 this connectiuu, are usually remarkably favourable for such 

 an investigation. Where, in other species, the tips are 

 perfect, it is often found that the septa are not determinable 

 until one or more metaseptal pairs have aj)peared, in addition 



The interseptal spaces are now preatly enlarged, and all the septa are 

 free from eacli other and from the dor.^al directive septum with its 

 colmnella-like free end. Exosepta regularly alternate with the 

 entosepta all round the calice, and the ventral directive septum is 

 a little smaller than the other principal septa, thus giving rise to a 

 fossula. The stage I'epreseuted is practically that characteristic of 

 the fully developed corallum. 



to the protosepta ; sometimes partial or entire silicification of 

 the corallum has taken place, and rendered the preparation 

 of sections practically impossible; while in such as Dancanella 

 horeah's the original tip is wanting, and when first collected 

 four, five, or six pairs of septa are frequently exposed to 

 view (fig. 17). 



Since the publication of my first paper I have made con- 

 siderable eff'orts to secure from various sources specimens of 



