lxiv BRITISH FOSSIL CORALS. 



Sub-order 4. 

 ZOANTHARIA RUGOSA. 



Corallum simple or composite, with a septal apparatus never forming six distinct 

 systems, as in all the preceding Zoantharia, but appearing to be derived from four primary 

 elements. Sometimes this disposition is rendered manifest by the existence of four well- 

 characterised primary septa, or of an equal number of depressions occupying the bottom of 

 the calice, and assuming a crucial appearance •. in other cases only one of these primary 

 septa or excavations is well developed so as to interrupt the radiate form of the system ; and 

 in others, again, no trace of septal groups can be discovered, and the whole apparatus is 

 represented by numerous equally developed radiate striae rising on the surface of the tabulse, 

 and extending up the inner side of the walls. The corallites are always perfectly distinct, 

 and are never united by means of a ccenenchyma ; nor do they ever form linear series, 

 which is often the case in the preceding sections. They multiply by gemmation, and the 

 reproductive buds are in general developed on the surface of the calices of the parents : 

 this often arrests the growth of the latter, and gives rise to a superposition of generations. 

 It is also to be noted that the septa, although in general very incomplete, are never porous, 

 and never bear synapticulae, but that the visceral chamber is in general filled up from the 

 bottom by a series of transverse tabula?, or by a vesicular structure, which often constitutes 

 the principal part of the corallum. 



Family XII. 

 STAURIDiE. 



Corallum with well-developed septa, extending without any interruption from the bottom 

 to the top of the visceral chamber, united by lamellar dissepiments, and arranged in four 

 systems, characterised by an equal number of large primary septa. 



1. Genus Stauria. 



Corallum composite, massive, astreiform, and increasing by calicular gemmation. 

 Corallites united by their walls, or free in part, and not presenting any costce. Septa large, 

 and with undivided edges, united along the axis of the visceral chamber. No columella. 



Typ. sp., Stauria astreiformis, nob. 



2. Genus Holocystis. 



Lonsdale, in the Quarterly Journal of the Geol. Soc. of London, vol. v, part i, p. 83, 1849. 



Corallum composite, massive, astreiform, and increasing by extra-calicular gemmation. 

 Corallites united by means of well-developed costce. Columella styliform. 



Typ. sp., Holocystis elegans ; Cyathophora elegans, Lonsdale, loc. cit., tab. iv, figs. 12, 13, 14, 15. 



