SUB-GENUS PERONOPORA. 231 



are shown in tan^fential sections to be due to bendino-s of the 

 wall of the coralHte, caused by the presence of the " spiniform 

 corallites " between adjacent tubes. Precisely similar irregu- 

 larities of the walls of the corallites are caused, in a similar 

 manner, in such Monticiiliporcs as ]\I. implicata^ Ulrich, and 

 AL frondosa, D'Orb. [ = M. dccipiens, Rominger). 



In the meanwhile, I think it is perhaps safest to provision- 

 ally refer the present form to the genus Monlicjilipoi-a, though 

 it certainly exhibits peculiarities which may ultimately lead to 

 its separation from the more normal types of this genus. At 

 any rate, I should not think it advisable to remove it from 

 Monticulipora proper without at the same time removing 

 elsewhere such forms as J/, frondosa, D'Orb., and AL ivipli- 

 cata, Ulrich, with which it shows a remarkable relationship in 

 internal structure, at the same time that its external form is 

 very different. 



Hovzion and Locality. — Common in the Cincinnati Group, 

 Cincinnati, Ohio. All the specimens I have seen are attached 

 to the valves of Strophomena alternata, Conrad ; and I believe 

 this to be its almost invariable habitat. 



