APHROPHYLLUM HALLENSE AND LITHOSTROTION. 



53 



is with few exceptions bounded by a mural investment — 

 the epitheca. 



The composite corallum may be fasciculate in growth- 

 habit, in which case the corallites are not in lateral contact, 

 and are consequently circular in section. On the other 

 hand, it may be massive, and the corallites in this case are 

 contiguous and are polygonal in section through mutual 

 pressure. The massive colony may be basaltiform, i.e. the 

 corallites, though contiguous, are defined by epitheca; or 

 may be astraeiform, i.e. the epitheca is absent, and the 

 corallites are confluent. 1 



Preservation of Material. 



The material is well preserved. The corals are embedded 

 in dark limestone, and the interstices are filled by clear 

 calcite. The tissue has re-crystallized to some extent, 

 and when examined through tiie microscope is seen to have 

 lost something of its definition. 



Aphrophyllum Hallensb gen. et sp. nov. 

 Plate II, figs. 1-5. 

 External Characters. — The corallum is composite, and 

 of massive growth-habit. The corallites are contiguous 

 but imperfectly so. They are turbinate in form. 



Internal Characters. — The corallites as seen in trans- 

 verse section are imperfectly polygonal in shape, for since 

 their contiguity is not absolutely perfect, and the mutual 

 pressure they exert is therefore not entirely uniform, their 

 outline is partly angular, partly rounded. (Plate II, fig. 1) 

 The largest corallites measured about 1*75 min. in diameter. 



The septa do not reach the epitheca except in very early 

 growth stages, in fact, in the mature stage they are not 

 prolonged very far beyond the theca. The major septa 

 extend to the centre of the corallum, and these give rise 



1 Q.J.G.S., Vol. lxxii, (1917) pp. 261 -282. 



