COL UMNARIAD^E. x 99 



the septa, these structures being divisible into a double series 

 of alternately long and short septa, of which the latter are quite 

 rudimentary and marginal, while the former vary greatly in their 

 development. Sometimes they fall short of the centre by a con- 

 siderable interval as is also usually the case in C. alveolata 

 but in other tubes they nearly or quite reach the axis of 

 the visceral chamber. Moreover, the phenomena which the 

 septa exhibit are precisely such as every student of the Rugose 

 corals is familiar with. The longer septa, namely, are not of 

 uniform length, but exhibit clear differences in their develop- 

 ment, almost amounting to that produced by the existence of 

 regular " cycles." Some of them quite reach the centre, others 

 fall a little short of it ; and there is even a tendency to the pro- 

 duction of a single predominant septum, or of two such, towards 

 the sides of which the remaining septa bend. Lastly, it is quite 

 common for the longer septa to be more or less united with one 

 another by their inner ends in a series of fascicles, though at 

 other times each may be quite free. 



Vertical sections of the corallum show no features of special 

 structural importance (PI. X., fig. 2 a). When they pass accu- 

 rately through the centre of the visceral chamber, the princi- 

 pal or only structures observable are the tabulae, which are com- 

 plete, essentially horizontal, though flexuous, and about six in 

 number in the space of two lines. On the other hand, when 

 the section passes at all out of the central line of the tubes, the 

 tabulae are cancellated by vertical lines representing the cut 

 edges of the septa. No mural pores have been detected. 



Formation and Locality. Abundant in the Cincinnati Group 

 (Hudson River formation) of the Credit River, Ontario. Dr 

 Rominger quotes the same species (under the name of C. 

 Hcrtzeri, Rom.) from the Cincinnati Formation of Kentucky. 



