150 THE VOYAGE OF H.M.S. CHALLENGER. 
* 
when the structure of the soft parts of such forms as Caryophyllia maculata are examined, 
it will be found to correspond closely with that of Caryophyllia, or at least show far 
more affinity to the Turbinolidee than to such simple corals of undoubted alliance to the 
Astreeidee as those composing the genus Avtillia 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. 1 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 tabula amongst Coelen- 
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 Flabellum, as will be described in the 
sequel. In some nearly allied species of the genus, such as Mlabellum stokes, Flabellwn 
patens, and Flabellum 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 Mlabellwm ; 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,” 
and the columella is alike in both forms. Lindstrém does not place Duncania with 
the Rugosa. It is probable that the non-demarcation of the septa into groups of sixes 
in these genera is of itself of small importance. Pourtalés has shown from the study 
of the structure of Lophophyllum proliferum that the septa are in that coral primarily 
arranged in sixes. On comparing specimens of Duncania with those of species of Theco- 
cyathus, there can scarcely be a doubt that it is most unnatural to separate widely 
‘G. Lindstrom Ofversigt af Vetenskabs, Akad. Forh., 1873, p. 30. 
