130 THE VOYAGE OF H.M.S. CHALLENGER. 



when the structure of the soft parts of such forms as Caryopliyllia maculata are examined, 

 it will be found to correspond closely with that of Caryopliyllia, or at least show far 

 more affinity to the Turbinolidae than to such simple corals of undoubted alliance to the 

 Astraeidse as those composing the genus Antillia for example. I have similarly neglected 

 the fact of the presence of dissepiments in placing Professor Martin Duncan's genus 

 Solenosmilia in its order in my list. It is most obviously closely allied to Lophohelia, 

 and might possibly with advantage be absorbed within it. A similar bigemmation in the 

 terminal calicles to that occurring in Solenosmilia may be not unfrequently observed in 

 the case of Lophohelia. I conclude that the presence or absence of dissepiments is pro- 

 bably of no more value as a criterion for the determination of the natural affinities of 

 various forms of Madreporaria than is the presence or absence of tabulae amongst Ccelen- 

 terates forming a corallum. 



Corals following the usual law as to early development, it necessarily occurs that 

 nearly allied species are in the young condition very closely alike, and sometimes indis- 

 tinguishable. In the very early stages the young of even widely different species of the 

 same genus are almost absolutely alike. I have had the opportunity of noticing this to 

 be the case, especially in some species of the genus Flabelhtm, as will be described in the 

 sequel. In some nearly allied species of the genus, such as Flabellum stokesi, Flabelhtm 

 patens, and Flabelhtm australe, the young remain alike even after they have reached a 

 considerable size. It is only in the larger adult form that their specific distinctness 

 becomes marked. They should not, however, for this reason be placed together on 

 the ground of apparent gradation into one another. 



No doubt some of the deep-sea corals here described may be identical specifically with 

 certain Tertiary fossil forms, or even older species, and I have reason to believe that this 

 may be the case with regard to more than one species of Flabelhtm ; but, unfortunately, 

 in so many instances the fossil specimens are so much obscured by the presence of 

 matrix, or so fragmentary, that none of the finer points, on which the question of specific 

 identity turns, can be discovered, at all events without great labour. I have, therefore, 

 in such instances merely noted the possibility of the identity of species described with 

 evidently allied fossil forms. 



It is probable that the genera Duncania and Thecocyathus are closely related. Both 

 have an epitheca, which grows out into hollow roots, and an internal " stereoplasma," 1 

 and the columella is alike in both forms. Lindstrom does not place Duncania with 

 the Eugosa. It is probable that the non-demarcation of the septa into groups of sixes 

 in these genera is of itself of small importance. Pourtales has shown from the study 

 of the structure of Lophophyllu m proliferum that the septa are in that coral primarily 

 arranged in sixes. On comparing specimens of Duncania with those of species of Tlieco- 

 cyathus, there can scarcely be a doubt that it is most unnatural to separate widely 



1 (j. Lindstrom Ofversigt af Vetenskabs, Akad. Forh., 1873, p. 30. 



