292 ZOANTHARIA. 



Carboniferous period, the principal genera being Clisiophyllum, 

 Dibunophyllum, Cydophyllum, Aulophyllum, and Lonsdaleia. 



In the genus Clisiophyllum the general structure of the simple coral- 

 lum is as described in the above characterisation of the family Clisio- 

 phyllidce. The great central pseudocolumellar mass is composed of a 

 number of tolerably regular, radial and somewhat spiral lamellae, which 

 may be regarded as corresponding with prolongations of the septa, and 

 which are intersected by obliquely directed vesicular tabulae (fig. 171, b). 

 As seen in the floor of the calice, the pseudocolumella forms a large 

 rounded boss, marked by spiral radiating ridges. The zone immediately 

 external to the pseudocolumella is occupied by inosculating tabulae, 





' llllllfl - '- W~mM^ : 



Fig. 171. — a, Cross-section of two corallites of Lonsdaleia duplicata, Lower Carboniferous, en- 

 larged ; b, Cross-section of the corallum of Clisiophyllwn Kcyserlingi, Lower Carboniferous, of 

 the natural size. (After James Thomson and the Author.) 



forming large vesicles ; and external to this region is a deep peripheral 

 zone of small oblique dissepimental vesicles, traversed by the septa. 

 The septa are numerous, alternately long and short, and a well-marked 

 septal fossula is present. The species of Clisiophyllum are probably 

 wholly confined to the Carboniferous period, though some Devonian and 

 Silurian corals have been referred here. 



The Carboniferous genus Dibunophyllum (fig. 170) is very closely 

 related in general structure to Clisiophyllum, out the pseudocolumellar 

 area is divided into two by a vertical partition, or columellar plate, 

 one end of which is usually connected with the " counter septum," while 

 the other is directed to the " cardinal septum " in the fossula, the bilateral 

 symmetry of the corallum being thus exceedingly well marked. Again, in 

 the Carboniferous genus Aulophyllum, and the nearly allied or identical 

 Cyclophyllum, the pseudocolumellar area is enclosed by a kind of inner 

 mural investment or accessory wall, and is prolonged at one point into a 

 lateral tongue-like extension directed to the fossula. The pseudocolumella 

 has a minutely vesicular structure, the vesicles being formed by radial 

 lamellae intersected by obliquely ascending arched dissepiments. Aulo- 

 phyllum stands in the same relation to Clisiophyllum that Crepidophyllum 

 holds to Heliophyllum, or that the Devonian Acervularioz (so-called) hold 

 to Cyathophyllum. 



