2(10 THE VOYAGE OF H.M.S. CHALLENGER. 



Iu a young specimen of this coral, without reference to which the true nature of the 

 complicated structures in the adult could hardly have been determined, the corallum is 

 almost symmetrically biconvex and perfectly circular ; but the columella is elongate, as 

 in the adult. The columella is papillar rather than laminar, and represents the rooted 

 base of the adult columella. There are sixty perfect costa? present at the margin of the 

 calicle, and the commencement of two more in each system (i.e., twelve in all). There 

 are twelve concentric rows of perforations in the base.- The septa are not nearly so 

 much contorted as in the adult, and the synapticular junctions between them not being 

 as 3^et formed, the division of the septal cavities into successive chambers is uot apparent 

 as in the adult. No superficial fusion of the primary with the curved extensions of the 

 tertiary and quaternary sejtta has as yet taken place ; hence no six-rayed star or flower 

 appears in the centre. Stout transverse granular projections are present on the upper 

 margins of the septa, the sources of future synapticular connections. Only four cycles are 

 complete in each system. Two members of the fifth cycle are present in each system, and 

 are those nearest the primary septa on each side. An additional pair of quinary septa is 

 just commencing to grow in each system, and branching off from the peripheral ends of 

 the quaternary septa which are next the secondary, but on that side of them which is 

 nearest the primary, i.e., opposite to the secondary. A very short branch of the costa 

 belonging to the interspace between the quaternary and secondary septa passes into each 

 interspace formed between these newly -grown quinary septa and the quaternary adjoining. 



In the development of a flower-like series of oval chambers around the elongate 

 columella, this coral most strikingly resembles Stephanophyllia florealis of Quenstedt, 1 

 which is a fossil of the " White Jura " ( = Oxford Clay) formation. The oval chambers 

 here in the first series around the columella are twelve in number, and alternate with 

 twelve in the second series. In Stephanophyllia complicata, six alternate with six. In 

 Stephanophyllia florealis there appears to be no trace of the bisection of these chambers 

 by the straight primary and secondary septa as in Stephanophyllia complicata; but the 

 fossil specimens are, according to Quenstedt, always so much mutilated that then struc- 

 ture can only partially be made out. Possibly the twelve chambers of Stephanophyllia 

 florealis may represent the twelve of Stephanophyllia complicata, formed by the bisection 

 of the six inner by the primary septa, which might appear as figured in Stephanophyllia 

 florealis in much-worn specimens. Comparison with actual specimens may determine 

 this point. In Stephanophyllia florealis forty-eight septa only are distinguishable; but 

 it is highly probable that structures so slight as the quinary septa of Stephanophyllia 

 complicata might be indistinguishable in a mutilated fossil. The coral appears to fall 

 into that division of the Stephanophyllias distinguished by Milne-Edwards as having the 



1 Milne-Edwards and Hainie, judging from Quenstedt's figure, Handb. der Petrefact, p. 657, pi. lix. figs. 12, 13, 

 1S52, wrongly supposed that Stephanophyllia florealis should be referred to the genus Thecocyathus, Hist. Nat. des Coral. 

 t. ii. p. 49. 



