.SUBCLASS II 



HEXACORALLA 



1)7 



readily becoming detached. Common in Triassic and Jurassic ; somewhat rare 

 in Cretaceous and Tertiary. The genus should probably be made to include 

 various species which have been referred to Epismilia From., and the so-called 

 Oppelismilia Duncan. 



ß. Simple cor a IIa or composite coJonies 

 iiiiiUiphjing hy calicinal or marginal gem- 

 ination. 



Sfijlophyllum Eeuss. Corallum simple, 

 either with or without calicinal or 

 marginal gemmation, or f orming massive 

 colonies. Septa stout, but only in- 

 feriorly complete, terminating above in 



strong vertical spines. Dissepiments vesicular ; wall covered with epitheca. 

 Alpine Trias. 



Stylophyllopsis Frech. Simple or imperf.ectly branching. Septa terminating 

 near the centre in detached vertical spines. Alpine Trias. 



Fifi. 138. 



MontltvdUia caryophyllata (Lamx.). Great Oolite : 

 Caen, Calvados. Natural size. 



Stylocora exilis Reuss. Mio- 

 ccne ; Niederleis, Austria. a, 

 Corallum in natural size. h, 

 Calice enlarged (after Reuss). 



Bushy colonies multiplying hy lateral gemmation. 



Cladocora Ehrbg. Corallum composed of long 

 cylindrical branches, free on all sides. Calice circular ; 

 septa well developed ; columella papillous ; cycle of 

 pali present. Jurassic to Recent. 



Stylocora Reuss (Fig. 139). Branches cylindrical; 

 septa stout, those of the first cycle with columnar 

 thickenings or inner edges ; columella styliform. 

 Cretaceous and Miocene. 



Pleürocora E. and H. Cretaceous. Goniocora E. 

 and H. Triassic and Jurassic. 



h. Composite corallites multiplying hy hasal gemmation ; huds arising from stolons 



or hasal expansions. 



Rhizangia E. and H. (Fig. 140). Corallites united by short, sub-cylindrical 



Fig. 140. 



Rhizangia michclini Reuss. Middle 

 Cretaceous ; Gosau Valley, Austria. 

 Natural size (after Reuss). 



Fio, 141. 



Viadang iaconferki Reuss. Miocene; Bischofs- 

 wart, Moravia. a, Corallum, natural size ; b, 

 Calice enlarged (after Reuss). 



Stolons. Calices shallow, circular; columella papillous. Cretaceous and Tertiary. 

 Latusastrea d'Orbigny. Corallites arising from common basal expansion, 

 Short and strongly inclined to one side, so that the calices acquire a semi- 

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