MADREPORARIA APOROSA. 



271 



Palaeozoic genera Heterophyllia and Battersbyia. In the former of 

 these (fig. 148) the corallites are long and slender, increasing by budding 

 around the calicular margin. There is a thick wall, marked by prominent 

 costae, which may be variously ornamented. There may be only six 

 septa ; but there is usually a larger number of these structures, their 



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Fig. 148. — Heterophyllia angulata, from the Carboniferous Limestone of Northumberland. 

 A, A fragment of the corallum, enlarged slightly, b, Transverse section of the same, enlarged 

 seven times, c, Longitudinal section, similarly enlarged : t Tabulae ; r Cut edges of the septa. 

 (Original.) 



arrangement being distinctly bilateral, and in many respects resembling 

 that seen in young examples of Zaphrentis. Some of the septa usually 

 became coalescent, so as to give rise to fan-like groups, while the longer 

 septa are continued to meet in the centre of the visceral chamber. There 

 is no true columella, but a "fossula" is often present (fig. 148, b) ; and 

 the septa are further peculiar in so far that the wall does not appear to 



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Fig. T^q.—IsastrcBa oblonga; portion of a small polished slab, of the natural size, and a few 

 calices enlarged. Jurassic (Portland Oolite). 



be formed by an extension and fusion of their outer ends. Lastly, dis- 

 sepiments in limited number are present, and curved " tabulae " are well 

 developed (fig. 148, c). The genus is only known as occurring in the 

 Carboniferous rocks of Britain. 



The genus Battersbyia (with which the Fascicitlaria of Dybowski may 

 be compared) was founded to include certain Devonian corals possessing 



