74 COELENTERATA—CNIDARIA SUB-BRANCH II 
of the thickened and fused septal edges ; sometimes it is invested with epitheca 
and furnished with vertical rugae or root-like processes. A true coenenchyma 
is absent. Ina few genera the calice is provided with a lid or operculum, 
which may be composed of one (Calceola) or of several plates (Goniophyllum). 
With the exception of a few genera whose systematic position is uncertain, 
all the typical Zetracoralla are confined to the Palaeozoic rocks. They are 
probably the ancestors of the imperforate Heaacoralla. 
Family 1. Cyathaxonidae. Milne-Edwards and Haime. 
Turbinate or horn-shaped coralla, occurring only simple. Septa with regular 
radial arrangement. Tabulae and dis- 
sepiments absent. 
Cyathaxonia, Mich. (Fig. 106). 
Acutely pointed, conical. Cardinal 
septum in fossula. Septa numerous, 
extending inward as far as the 
strongly developed styliform and 
considerably elevated — columella. 
Carboniferous Limestone ; Belgium 
and England. 
Duncanella, Nich. Corallum top- 

Fic. 106. shaped. Septa nearly all of uniform 
Cyathavonia Fic. 107 leneth and size, forming a spurious 
Mich = ; = 
cornu, q mls . . 
Carboniferous Petraia radiata, columella in centre of the deep calice, 
Limestone; Mnst. Devonian ; ey ae Ot], <1 See pa ene 
Tournay. Cor- Enkeberg, near exsert at the base. Silur 1an ) N or th 
allum with Brilon. 1/3. a, Cor- Polycoelia pro- America. D. borealis. Nich. 
fractured theea, allum viewed from funda, Germ. 2 
showing open the apex; 0, Trans- sp. Zechstein; Petraia, Miinst. (Fig. 107). Tur- 
interseptal verse section below Gera. 1/; (after : x : : 
loculi. or the middle. Roemer). binate o1 conical, Septa sho t, 
reaching to the centre only at the 
base of the very deep calice. Columella absent. Ordovician to Carboniferous. 
Polycoelia, King. (Fig. 108). Horn-shaped. 
Calice very deep; four principal septa reach 
nearly to its centre, between which in each 
quadrant are five shorter septa. Zechstein. 
Kanophyllum, Dyb. Ordovician and Silurian. 
Family 2. Palaeocyclidae. Dybowski. 
Coralla simple, discoidal, or bowl-shaped. Septa 
numerous, stout, approaching radial syminetry im 
disposition.  Tabulae and dissepiments wanting. 
Palaeocyclus, E. and H. (Fig. 109). Discoidal 
to depressed top-shaped, with epitheca, Septa 
numerous, radially disposed, the larger ones 

Fic. 110. 
Microcyclus 
discus, Meek and 
Worth. Hamil- 
ton (Devonian) ; 


Fic. 109. 
Re Palaeocyclus por- North America. 
eae ; 2 > +i oF pita, Lin. Silurian; 1}. a, Corallum 
reaching to the centre. Silurian. Ee Oto Se ee 
Combophyllum, Baryphyllum, E. and H. view of calice; 0, from above 
: s ’ : b, Profile. 1/;. (after Nicholson). 
Devonian. 
Hadrophyllum, E. and H. Cushion-shaped, with epitheca. Calice with three 
septal fossula, that of the cardinal septum being the largest. Devonian ; Eifel 
and North America. 
