PROBLEM OF THE M0NT1CULIP0R0IDEA I 73 



There is an accompanying differentiation from uniformity in 

 the first instance to marked axial and peripheral region of the 

 cell in the fourth and other characters incidental therewith. 

 But all things considered the monticules and their special form 

 maculae, are all that separate the Monticuliporoidea from other 

 Tabulate (Alcyonarin) corals, but apparently not from certain 

 living Alcyonaria, which have possibly descended from them. 



As to Bryozoa, two hypothetical comparisons with Monti- 

 culiporoidea are to be considered. First, the Cerioporidse includ- 

 ing Heteropora, may be Bryozoa derived from Monticuliporoidea 

 in the first instance just mentioned, the solid wall having become 

 porous with transverse canals. Secondly, Berenicea and other 

 Bryozoons with more or less free vestibules might have derived 

 from the fourth instance, being then a fifth stage or instance, 

 the mesopore solid filling having reduced to nothing and imper- 

 forate cells walls having become perforate. 



The Monticuliporoidea are difficult to separate from corals 

 in two concordant instances. In two instances in which their 

 structures nearest approach the Bryozoa, they separate easily or 

 rather are difficult to unite with them, and of these instances the 

 one probably negatives the other. 



EXPLANATION OF PLATE B. 

 Fig. 1. Pachydictya foiiata, frond natural size. 

 Fig. 2. Pachydictya foiiata, longitudinal section. X 10. 

 Fig. 3. Pachydictya foiiata, tangential section. X 10, showing cell pattern. 

 Fig. 4. Rhinidictya mutabilis, frond of an undersized individual. 

 Fig. 5. Rhinidictya mutabilis, part of surface. X 20, after Ulrich. 

 Fig. 6. Rhinidictya mutabilis, longitudinal section. X 10. 

 Fig. 7. Stictoporella cribrosa, lower part of frond with articulation. 

 Fig. 8. Stictoporella cribrosa, surface. X 20. 

 Fig. 9. Stictoporella cribrosa, longitudinal section. X 20. 

 Fig. 10. Ptilodictya subrecta, surface. X 20 showing zoarial margin. 

 FlG. 11. Phylloporina corticosa, part of basal expansion and one 

 frond. X 2. 



Fig. 12. Phylloporina corticosa, longitudinal section. X 20. 



Frederick W. Sardeson. 



Minneapolis, Minn., 



November 5, 1900. 



