EXPLANATION OK l'LA'rp:S o<)0 



Plate 21. — Development ok the Monticuliporoids 



Figure 21. — Vertical Section throuyh the initial Region of a Colony of Praso- 

 pora conoidea. 



Showing a portion of tlie protoeciiun and the ancestrula. Most of the 

 protoecium has been weathered away (cf. figure 23). The bud e arises to 

 one side of the aniestrula and not from the ancestrula. The peculiar 

 thickened wall of the ancestrula is also well shown, x "*•'• IMiylloitorina 

 bed, Cannon Falls, Minnesota. (104-14.) 

 Figure 22. — Semi-diagrammiatic Draicinf/ from Fiitnre 21. 



Figure 28. — Vertical Section throuf/h the initial Reyion of another Specimen 

 of Pranopora conoidea from the same fjocality. 



The entire protoecium is shown in this specimen. Its perfectly circular 

 outline (cf. figure 9) could be seen on the base of the colony before the 

 section was cut. X 43. (lOG-14.) 

 Figure 24.— .4 Section of the same Specimen as Fiyure 23. 



Made in a plane i>arallel with and slightly to one side of the latter sec- 

 tion. This section shows how the bud e arises well to one side of and 

 laps over the ancestrula and i>rotoeciinii. Its tip is also elevated con- 

 siderably above the substratum, x -^•^>- 

 Figure 25. — Transverse Section throuyh the initial Reyion of Prasopora conoi- 

 dea at the Level r-r', Fiyure 20. 



Showing the protoecium, ancestrula, and primary buds. Note that the 

 tip of the bud f is not in contact with the ancestrula. x 43. Phyllo- 

 porina bed, Cannon Falls, Minnesota. (104-21.) 

 Figure 26. — Semi-diayrammatic Drairiny from Fiyure 25. 



Figure 27. — Semi-diayrammatic Dran'iny of a similar Section of another Speci- 

 men of P. conoidea from the same Locality. 



In figures 26 and 27 the probable dei'ivation of the buds is shown by the 

 arrows. The broken arrows indicate an alternative interpretation of the 

 derivation of the buds e and f. x 43. (104-16.) 

 Figure 28. — Portion of a youny Colony of the recent Bryo.zoan Mrmhranipora. 

 after Barrois. 



To show the identity of the budding pattern with that of the Treposto- 

 mata. x '<'%• 

 Figure 29. — Transverse Section throuyh the initial Region of Phylloporina 

 corticosa. 



Showing a beautifully preserved protoecium, ancestrula, and primary 

 buds. Note the striking similarity to similar sections of Prasopora. X 43. 

 Phylloporina bed. Cannon Falls, Minnesota. (56-7.) 

 Figure 30. — Draiciny of the recent Pryozoan Tuh'ulipora, after Barrois. 



For comparison with figure 29 and figures 7 and 8. x 40. 

 Figure 31. — Transverse Section through an Adult Colony of Prasopora conoi- 

 dea at the Level m-m', Fiyure 20. 



Same section as figure 32. x 43. Phylloporina bed. Cannon Falls. Min- 

 nesota. (104-24.) 



