(J. E. Beecher — Development of a Paleozoic Poriferous Coral. 213 



EXPLANATION OF PLATES. 



Plate IX. 



Pkurodictyum lenticulare. 

 Lower side of initial cell, or nepionic stage. x ?,^. 

 Lower side of initial cell with one bud ; first nealogie stage, x 3i. 

 Initial cell with two buds ; second nealogie stage, x 3^. 

 Initial cell with three buds; tliird nealogie state, x 3i. 

 Initial cell with four buds ; fourth nealogie stage, x 3^. 

 Completed nealogie stage; shouing initial corallile (!) and seven peripheral 



corallites (2 -8). x 3^. 

 Interior of nepionic corallite. x 3^. 

 Exterior of same specimen x 3^. 



Upper side of specimen representing first nealogie or Auhpora -stage, con- 

 sisting of nepionic cell and one bud Apex of bud opens into visceral 

 cavity of parent cell, x 3i. 

 Fig. 10. Profile of same; showing obliqne apertures of corallites, and thickened 



margin of parent cell x 3|. 

 Fig, 1 1. Lower side of preceding, x 3i. 

 Fig. 12. Upper side of completed nealogie stage; showing inception of eighth cell. 



Figs. 1-G are taken from epilhecal lines of growth shown in Plate X, figure 

 2. Remaining figures are from actual specimens. Numbers refer to 

 order of calical succession. 



Lower Helderberg Group. Albany County, New York. 



Plate X. 



Pleurodictymn lenticulare. 



Fig. 1. Lower or epithecal side of specimen; showing successive alternate gemma- 

 tion from parent coralHte. x 3^. 



Fig. 2. Similar specimen with lines of growth more strongly marked. The order of 

 luidding is opposite to that of preceding specimen, x 3^. 

 Lower Helderberg Group. Albany County, New York. 



Plate XL 



Pleurodidyum lenticulare. 

 Fig. -1. Outline of cahces of specimen Plate X, figure 2; showing central primary 

 cell and seven peripheral calices numbered in tiie order of their develop- 

 ment, x 3f . 

 Fig. 2. The same ; side view. 



Lower Helderberg Group. Albany County, Neiv York. 



