1 84 TABULATE CORALS. 



Nyctopora Billingsii, Nicholson. 

 (PI. IX., figs. 3 - 3 ^0 

 Columnaria Goldfiissi, Nicholson, Sec. Rep. Pal. Ont., p. 9, 1875. 



Spec. Char. — Corallum forming small spheroidal or pyrlform 

 masses, varying from seven lines in diameter and four lines in 

 height, to rather more than an inch and a half in diameter and 

 an inch in height. Corallites prismatic or polygonal, subequal, 

 about three-quarters of a line or rather less in diameter, their 

 walls everywhere contiguous and closely amalgamated. Septa 

 in the form of from eig^ht to twelve or more stronof marg-inal 

 ridges, which run the entire length of the tubes, and project to 

 a very limited extent into the interior of the visceral chamber. 

 Mural pores numerous, minute, circular, apparently not arranged 

 in any definite order. Tabulae horizontal, complete, about six 

 in the space of two lines. 



Obs. — As I have discussed the structure of this coral in 

 dealing with the genus Nyctopora, of which it is the only known 

 representative, I have little to add here. The specimens in 

 my possession are all from the Trenton Limestone of Canada, 

 and they were identified by me, from an external examination 

 only (Sec. Rep. Pal. Ont., p. 9), as young examples of Cohim- 

 7iaria Goldfnssi, Bill. They agree, indeed, with the descrip- 

 tion of this species (Geol. Surv. Can. Report of Progress for 

 1857, p. 166, 1858) in most respects, but the latter is said to 

 form " large amorphous or subglobose masses," with from four 

 to six tabulae in the space of one line, the septa " rudimentary, 

 but distinctly striating the interior walls ; " whereas the present 

 form is always quite small, its tabulae are wider apart, and its 

 septa, though rudimentary, have the form of strong vertical 

 ridges. As it is not known whether or not mural pores are 

 present in Columnaria Goldfussi, Bill., no stress can be laid 

 upon this character ; but their undoubted presence in Nyctopora 

 Billingsii, taken along with the differences above noted, and 



