72 Cumings — Development of some Paleozoic Bryozoa. 



Polypora, but outward and away from the axis in Fenestella, 

 In normally developed Fenestella cones, therefore, the zomcia 



71 72 73 



74 



76 



75 



77 



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Figures 71-77. — Nepiastic stages of Polypora* 71-76. Young individuals 

 showing the protoeciuni (*) and primary buds (I, I, I) and the beginning of 

 the primary branches (a to g). Fig. 74 (paranepiastic stage) shows the latter 

 feature very perfectly. 77. Section through the base of an individual from 

 Thedford, Ontario, showing protcecium (*) surrounded by seven zooecia, five 

 of which are in contact with it. Ii, I 2 , and I 3 must have arisen from the 

 protcecium. 



Figures 71-74 x 26 ; figures 75-76 x 30 ; figure 77 x 13. 



are always on the outer surface of the cone, while in normally 

 developed Polypora cones the zomcia are always on the inner 

 surface of the cone. The type is determined by the position 

 and orientation of the primary buds. 



* Compare with these figures, Ulrich's figures of Sphragiopora. Geol. 

 Sur. Illinois^viii, pi. Ixv, figs. 6, 6a. 



