159 



CHAPTER VI. 



GENERA OF FAVOSITID/E {contmued). 



Genus Columnopora, Nicholson, 1874. 



(Geol. Mag., new sen, vol. i. p. 253, fig. i.) 



Hoiightonia, Rominger, Foss. Cor. of Michigan, p. 17, 1876. 



Gen. Char. — Corallum massive, forming subhemispherical or 

 pyriform masses, often of considerable size, composed of sub- 

 polygonal or subcircular corallites, which radiate from the base, 

 and are for the most part in contact and firmly united by their 

 walls. Septa in the form of marginal ridges, generally about 

 twenty in each corallite. Walls thick, perforated by numerous 

 large, close-set, oval mural pores, arranged in rows between the 

 septal ridges. Tabulae numerous, generally more or less flexu- 

 ous, often uniting with one another, complete. No columella 

 and no true coenenchyma. 



Obs. — The corallum in this genus is massive, and in general 

 aspect very similar to that of any of the larger species of 

 Favosites, though distinguished from the latter even by a very 

 cursory examination. The corallites are in reality subpolygonal, 

 but the angles of the tubes are more or less rounded off, 

 and they thus become subcircular in form (PI. VII., fig. 2). 

 The real structure of the corallum can be best investigated by 

 means of transparent sections, though many of its most import- 

 ant features can be studied in the actual specimens. The coral- 



