PROBLEM OF THE MONTICULIPOROIDEA 5 



then has to do with the most problematic as to affinities of the 

 so-called Paleozoic Bryozoa, i. e., those which most resemble 

 corals^ proceeding then to those often supposed to be true 

 Bryozoa, the Cryptostomata. Eastman's manual, op. cit., includes 

 them in the arrangement given below, and in the Order Gymno- 

 laemata, which comprises most Bryozoa and all known fossil 

 ones. Of those five divisions, the last named, Chilostomata, are 

 all undoubtedly Bryozoa, but are not known in the Paleozoic 

 rocks. The first, Cyclostomata, are, with few possible excep- 

 tions, all true Bryozoa, but few of them are Paleozoic. The 

 second, third, and fourth comprise the Monticuliporoidea. 



i. Cyclostomata (8 families). 



2. Families doubtfully referred to Cyclostomata (4 families). 



3. Trepostomata (7 families). 



4. Cryptostomata (8 families). 



5. Chilostomata (13 families). 



In that arrangement those of doubtful affinities are embraced 

 between the true Bryozoa. A fairer presentation of the problem 

 may be given thus : 



Tabulata (corals) Trepostomata (?) Cyclostomata (bryozoa) 



Cryptostomata (?) Chilostomata (bryozoa) 

 and it is in such association that the Monticuliporoidea should 

 be studied. The group of " Doubtfully referred to Cyclosto- 

 mata " are Trepostomata. 



Beginning with one of the simpler Trepostomata, 

 Monotrypa magna Ulr. has a skeleton or zoarium one or two 

 inches in diameter, composed of tubes or "cells" which radiate 

 from an approximate center. It is nearly spherical if growing 

 attached on one point, or discoid if on a flat surface, or, again, 

 irregular. The center is the initial or oldest part, and from it 

 one, or practically several, cells arise, and as these extend, 

 others intercalate , successively. A specimen divided radially 

 (PL A, Fig. 2) shows parallel, approximately equal, cells, each 

 tapering to a point at the inner end. The plan of growth is that 

 of increase in number of cells proportionate to the increase in 

 size of the zoarium. At the surface, the open cell ends are 



