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182 Fossil Oorals of the family Cyathophyllide. 
adjacent polyps coalesce and produce solid massive forms. Ina 
few, the polyps are crowdedly in contact without coalescing, (or 
are united by their non-secreting exterior,) and in consequence 
of the mutual, pressure, have a prismatic form; and the coralla, 
though apparently solid, may be readily broken into prisms. The 
same genus, as in other departments of Zoophytes, may contain 
both solid, branching, and also simple or non-budding species. 
A study of the internal structure. of these corals, has led the 
writer to some changes in the received limits of groups, and also 
to the introduction of one or two new genera. ‘The generic 
names of older authors have, in some instances, of late been mis- 
applied ; in obedience to the principles relating to nomenclature, 
digested and brought out by the British Association, a restoration 
to their original characters has been attempted; and where im- 
practicable, their rejection seemed preferable to. retaining them 
with altered characteristics. : 
Other errors have arisen from regarding external forms too im- 
plicitly, in drawing out generic distinctions. 'Thus the genera 
Lithodendron and Columnaria, as employed, include species which 
are true Cyathophylla, and some allied species have been referred 
to the genus Caryophyllia (Cladocora, of Ehrenberg,) although 
differing totally from them and all others of the Caryophyllide, 
in the transverse structure of the interior. 
The following are the genera of this family, with their char- 
acters, In presenting this review of them, the author is aware 
that the subject requires much farther study before its difficulties 
will be wholly removed. We may subdivide them into the fol- 
lowing groups. 
1. Those with the cross septa transverse or but little oblique } 
sometimes nearly or quite obsolete. Includes the genera Cyatho- 
phyllum, Calophyllum, Amplexus, Caninia, Acervularia, Arach- 
nophyllum, Cystiophyllum. 
2. Those with the septa very oblique upward, and converging 
to a central line, with sometimes a distinct avis. Includes the 
genera Clisiophyllum, Michelinia, Columnaria, and Sarcinula. 
I. Transverse septa straight, or but little oblique, sometimes be- 
coming obsolete. 
Genus 1. Cyaruornytium. Quite simple, ramose or glome- 
tate. Corallum within transversely septate ; cells concave, regu- 
