GENERA OF FAVOSITIB^. i6i 



specimens themselves. They have the form of from fifteen to 

 twenty or more longitudinal ridges, which have broad bases, 

 and extend only a very limited distance inwards towards the 

 centre of the visceral chamber. The tabulae are seen in verti- 

 cal sections (PI. VII., fig. 2 c) to be complete and numerous, 

 more or less flexuous, and often uniting to a limited extent with 

 one another. They do not, however, carry this process of 

 anastomosis so far as to give rise to anything like the " sub- 

 vesicular " tabular tissue of Michelinia. Lastly, the mural pores 

 are seen both in transverse and longitudinal sections, though 

 best in the latter. In transverse sections (PI. VII., fig. 2 a) 

 they appear as transverse channels crossing the walls, and allow- 

 ing contiguous tube-cavities to communicate. In vertical sec- 

 tions they are only seen where the plane of the section may 

 happen to coincide with that of one of the walls of the tubes, 

 and then they are seen to have the form and arrangement ob- 

 servable by the ordinary methods of examination in the actual 

 specimens. They appear, namely (PI. VII., figs. 2 c and 2 d), 

 in the form of numerous longitudinally-placed oval pores of 

 large size, which occupy the interseptal spaces, and place the 

 visceral cavities in direct and free communication. The num- 

 ber of these pores in a given space is not absolutely uniform 

 in all parts of a given specimen ; but they are usually placed 

 at much less than their own diameter apart, measured both 

 vertically and laterally, so that the walls become completely 

 cribriform. 



In his excellent work upon the Fossil Corals of Michigan, Dr 

 Rominger, in 1876, founded the new genus HoiLghtonia, to in- 

 clude certain corals from the Cincinnati group of North Amer- 

 ica, which I cannot doubt to be really congeneric with the 

 previously described Coliimnopora. Indeed, Dr Rominger has 

 himself admitted this identity in a note appended to a later 

 edition of the same work (1877). In his description of the 

 genus Hotightonia, as originally published, and in the note just 

 alluded to, in which he admits that this name must be abandoned 

 in favour of Cohmmopora, Dr Rominger states that the coral- 



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