i87 



CHAPTER VII. 



COLUMNARIAD^ (lYOPORA AND COLUMNARIa). 



Gemts Lyopora, Nich. and Eth. jun., i 

 (Mon. Sil. Foss. of Girvan, Fasc. i. p. 25.) 



Gen. Cha7\ — Corallum composite, massive, forming irregu- 

 larly spherical or pyriform masses, composed of tubular, sub- 

 cylindrical, or subpolygonal corallites, which are more or less 

 completely fused with one another. Walls of the corallites 

 extraordinarily thick and dense, apparently destitute of mural 

 pores. Septa rudimentary, marginal, few in number, having 

 the form of irregular obtuse ridges on the interior of the wall. 

 Tabulae strong and complete. No columella nor coenenchyma. 

 Obs. — The corallum in this genus is chiefly remarkable for 

 the great density of the walls of the corallites, contiguous tubes 

 being separated by partitions which may equal half or more of 

 diameter of the former (PI. IX., figs. 2 and 2 a). Moreover, 

 the walls of neighbouring tubes are completely amalgamated 

 with one another, so that the original boundaries of the coral- 

 lites are either quite irrecognisable, or can only be made out 

 more or less obscurely. Rough fractures, also, invariably 

 expose the interior of the tubes. The corallites are subpoly- 

 gonal or subcircular in shape, and are essentially in contact 

 throughout their entire length. The dense intertubular scler- 



