<. 



220 



NEW YORK STATE MUSEUM 



Edwards and Haime iMonograpliie des poly piers fossiles. 1851. 

 p. 418), in the description of A c e r v u 1 a r i a d a v i d s o n i, 

 speak of the interior wall, but those forms which in this country 

 have been fjrenerallY considered as A. d a v i d s o n i do not have 



_ m 



Fig. 43 P r i s m a t o p li y 1 1 u m ( d a v i d s o n i ) E. and H. Trans- 

 verse section showing prismatic form, the septa, and the cut margins of 

 cysts, enlarged 



44 P. r n g o s u m E. and H. Transverse section showing polygonal 

 form of corallitcs and denticulated septa, enlarged 



45 Longitudinal section showing internal structure 



an interior wall, thouj^h in a transverse section the abrupt ending 

 of the cysts, or dissepiments, coincidentally with the shorter 

 septa gives the appearance of an interior wall. The continuation 

 of alternate septa to the center proves that there is no secondary 

 wall. 



