SUB-CLASS II ANTHOZOA—HEXACORALLA 81 
concerned in the formation of these reefs were Cyathophyllum, Heliophyllum, 
Omphyma, Piychophyllum, Strombodes, Acervularia, Stauria, Aulacophyllum, Cysti- 
phyllum, ete., of the Tetracoralla, besides numerous Tabulata, Octocoralla, Bryozou, 
and Echinoderms. The Yetracoralla are not less conspicuous in the Devonian, 
especially in the Middle and Upper Devonian of the Eifel district, Westphalia, 
Nassau, Harz, Boulogne, England, and North America. Particularly abundant 
here are the genera Cyathophyllum, Combophyllum, Zaphrentis, Cystiphyllum, 
Phallipsastraea, Calceola, ete. Zaphrentis, Amplexus, Lithostrotion, Lonsdaleia, Cyclo- 
phyllum, etc., predominate in the Carboniferous Limestone of Belgium, England, 
Ireland, and North America ; while in the Zechstein the solitary genus known 
is Polycoelia. On the other hand, the Permo-Carboniferous rocks of the Salt 
Range in Farther India and of the island Timor contain the genera Zaphrentis, 
Aimpleaus, Clisiophyllum, and Lonsdaleia. According to Frech, the genera 
Gigantostylis, Pinacophyllum, and Coccophyllum, occurring in the Alpine Trias, 
belong to the Tetracoralla ; and to this group also have been assigned Holocystis, 
E. and H., from the Cretaceous, and the recent genera Haplophyllum, Pourtales, 
and Guynia, Duncan. A number of Palaeozoic Tetracoralla, such as Battersbyia, 
Heterophyllia, and Stauria, are referred by Duncan and Nicholson to the Heau- 
coralla (Astraeidae). 
Sub-Class 2. HEXACORALLA. Haeckel. 
(Zoantharia, Blainville ; Hewvactinia and Polyactinia, Ehrenberg.) 
Simple or composite polyps, with radial mesenteries arising in cycles of six, twelve 
or multiples of six; frequently with calcareous { 
corallum, but sometimes fleshy or with horny 1 6483957275938 461 
: +10 212215 :13:14:17:16 211 : 11:16:17 14:13 :15:12:10: 
avis. ; 
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To the Hexacoralla belong the calcareous | 
reef-building and deep-sea corals (Madre- \ 
poraria) of the present day, the fleshy sea- ° 
anemones (Actiniaria), and those forms 
characterised by the secretion of a horny 
axis (Antipatharia). Of these three orders, 
only the Madreporaria are known in a fossil 
state. These forms are distinguished from 
the Tetracoralla by the hexameral system 
and radial arrangement of mesenteries and 
septa ; and from the Octocoralla, in addition 
to the above-named characters, by their 
simple tentacles. In the Madreporaria, six, = ee - 
pe more rarely twelve principal septa Sprime Diagram Alustrating Miles Hapa de and 
from the base of the theca, and between Haime’s law of septal growth in the Hexucoralla. 
these new septa originate in such manner 3; Gate Hite thee tools Rlaeed o Bor! 
that all similarly situated mesenteries be- ™men' of calice with six cycles of septa. (The 
numerals above Fig. ¢ indicate the order of inser- 
come simultaneously provided with an tion of new septa. The concentric dotted lines 
Oc mark the beginning and end of the several cycles ; 
additional septum. The corallum, accord- the figures on the left indicate the order of cycles, 
© : sim . and are placed opposite the line touched by the 
ingly, consists of at least six, but usually Poprunnaie civer cycle) 
of a larger number of septa, whose disposi- 
tion is strictly radial. The six principal septa form the first cycle, and at the 
VOL. I G 


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