492 



ME. H. M. BEENAED ON 



no compreliensive survey has ever yet been attempted. Milne- 

 Edwards and Haime described them as usually hardly distinct 

 from the pali.* I give, in the accompanying diagrams, a series 

 of their more important variations. These are found so in- 

 timately linked together, more than one being observable on 

 the same stock, that no generic distinctions can possibly be 

 built upon them. 



1. Twelve distinct septaend freely andseparately round the fossa. 



Diagrams showing the principal variations in the septal and palic 

 formula in Porites. 



Slight swellings of their inner edges may or may not indicate a 

 disposition to form pali. They may or may not be distinguishable 

 into two cycles. Forms with such septa, of which the best known 

 example is P. astrceoides, Lamarck, were grouped into a separate 

 genus t Neojporites by Duchassaing and Michelotti. But the 

 disposition to form pali and also to pass into the condition shown 

 in fig. 2 renders it impossible to admit any such distinction. 



* Ann. Sci. Nat. 3rd ser., xvi. 1851, p. 25. 



t Or 'subgenus,' Pourtales, Bull. Mus. Comp. Zool. iv. 1871, p. 85. 



