COL UMNARIAD^. 



20I 



the Columnaria alveolata of Goldfuss, and it is therefore best 

 to give the present species a distinct title rather than to per- 

 petuate a source of endless confusion. I am the more inclined 

 to take this course, as I am disposed to doubt very strongly if 

 the present form can be referred to Columnaria at all, and 

 whether it is not truly a perforate coral, congeneric with 

 Nyctopora, Nich. The material in my hands is, however, 

 not sufficient to setde this point finally. All that I can 

 affirm is that Cohimnaria (?) Halli agrees with Nyctopora 

 Billingsii, Nich., precisely in its general form and aspect, in 

 the complete amalgamation of the walls of the corallites, and 

 in the fact that the septa have the form of blunt marginal 

 ridges, not divisible into a double series. In all these points 

 C. (?) Halli differs from the true C. alveolata, Goldf , and from 

 the allied C. calicina, Nich. I am disposed also to think that 

 I can detect in thin vertical sections of C. (?) Halli small 

 mural pores, such as are so abundant in Nyctopora Billingsii. 

 On the existence, however, of this crucial character, I must at 

 present speak with much reserve, for the state of preservation 

 of my specimens is such that I have not succeeded in obtaining 

 from them any microscopic sections that could be confidently 

 relied upon as deciding a point of such delicacy and importance. 

 Leaving the existence of mural pores an open question, I 

 have little to add to the 

 above specific diagnosis 

 of C. (?) Halli. The gen- 

 eral form of the corallum 

 (fig. 29) is very similar to 

 that of C. alveolata, Goldf, 

 though the colonies most- 

 ly tend to assume a flat- 

 tened and laterally ex- 

 panded form. The coral- 

 lites are always polygonal 

 and prismatic, of very un- 

 equal sizes, but invariably in close contact throughout, and with 





fZ£j 



Fig. 29. — A small colony of Columnaria (?) Halh, 

 Nich., from the Trenton Limestone of Canada, 

 of the natural size. (After Billings.) 



