North American Palaeozoic Bryozoa. 



Classification. 



In determiriing the systematic position of the forms described 

 in this paper, the form and manner of growth of the zoarium as 

 a whole, as well as that of each cell, has been considered. 



It is best not to give too much weight to microscopical charac- 

 ters, which not one student in ten can detect, to the neglect of 

 more obvious characters, which can be observed by any student 

 of ordinary scientific penetration. This is especially true of 

 those forms which have undergone fossilization, and the con- 

 sequent modification of microscopic characters. 



It is a well-understood fact that one making a special study of 

 a certain group or groups can see minute differences which can 

 not be distinguished by others ; not that they do not exist, but in 

 order to distinguish them it needs constant and close study of 

 that particular group ; and it is apt to be the case that in the 

 study of these minute differences more important points of 

 agreement are overlooked. 



In many forms, as Stiotopoea, the cells, from their manner of 

 growth, need some support. In some species this support is pro- 

 vided for by a vesicular tissue between the cells ; in others 

 the space between the cells is filled up by an apparently, but not 

 in reality, solid mass. As the structure in either case is simply 

 for the support of the individual cells, if in other respects the 

 zoarium and zooecia are essentially the same, such difference in 

 the supporting structure can make but little difference in system- 

 atic position of the two forms ; certainly not a generic difference. 



Though the Montiouliporid^ and allied forms are described 

 here, there is but little doubt that all the forms which are 

 here placed in the family AMPLExopoKiDiE and other allied forms 

 are not Bryozoa. Any form which increases by fissiparity or 

 by coenenchymal gemmation, must of necessity be considered as 

 a Coral. 



