Genera of the North American Palaeozoic Bryozoa. 567 



tubes ; cells tubular, cylindrical, arising from the epitheca, and 

 for about one-half their length parallel with it, then abruptly 

 turning outward and opening obliquely to the surface ; apertures 

 oval, more or less regularly alternating and imbricating ; pos- 

 terior portion of the peristome strongly elevated and cucullate, 

 projecting over and partially concealing the apertures, with two 

 minute denticulations ; surface with frequent maculae destitute 

 of cell apertures, the maculae immediately adjacent to them 

 being larger than the others and radiating. 



THE MONTICULIPOROIDS. 



The systematic position of many of the forms which have been 

 included in the families Montioulipobid^ and Fistdlipokid.e has 

 been the subject of much discussion, and authors are not now 

 agreed whether they should be placed with the Br?ozoa or 

 the Corals. Although in this work they have been placed with 

 the Bryozoa, undoubtedly further study and investigation will 

 show that some of the forms at least must be associated with 

 the corals. 



Prof. H. A. Nicholson has made a close study of these forms, 

 and in his Manual of Palaeontology, Yol. I, p. 352, he sums up 

 the matter as follows : 



" It must be admitted, however, that the zoological affinities of 

 the Monticuliporoids is still a matter of uncertainty ; in many of 

 their features, both structural and developmental, they show 

 marked relationship with the Actinozoa generally and with the 

 Alcyonaria in particular, while in others they approach the 

 PoLYzo^, and iL must in the meanwhile remain a matter of indi- 

 vidual opinion whether the Monticuliporoids should be con- 

 sidered as a very peculiar group of corals or an equally peculiar 

 group of PoLYzoA. * ^ * Leaving the external form of the 

 skeleton entirely out of consideration, the general features which 

 favor the reference of the Monticuliporoids to the Coelenterates 

 is as follows : 



1. The common, dimorphism of the colony in the Monticu 

 liporoids finds its best parallel in Heliopora and Heliolites, the 

 coelenterate nature of which is undoubted. In particular the 

 structural relationship between Fistulipoka. and Heliolites or 

 Plasmopora are exceedingly close, the skeleton in both consisting 



