Genera of the ^orth American Palaeozoic Bryozoa. 569 



2. Tabulae are by no means confined to the Coelenterates, 

 precisely similar structures, so far as appearances go, being present 

 in undoubted Bryozoa {e. g. in Heteropora, Lomopoea, Faboiou- 

 labia, Alveolaria, etc.) 



3. Kadial structures in the form of rows of spines are present 

 in a number of Bryozoa {e. g. Heteropora, Disooporella, etc.) 



4. There are various Bryozoa, such as Rhombopora, Ceriopora, 

 and some of the Fenestelloids which possess structures very 

 similar to the " acanthopores " of many Monticuliporoids. 

 Structures possessing in some degree the same aspect, are found 

 in the recent RETEPORiDiE, where they serve to carry the 

 avicularia. 



5. Portions of the skeleton of Fistulipora incrustanshSjYe been 

 shown by John Young, to become thickened and to exhibit a 

 finely tubular structure, similar to that seen in the skeleton of 

 Fenestbllid^e. 



6. According to Lindstrom, certain of the Monticuliporoids 

 pass through early stages of development in which the skeleton 

 is a distinctly Bryozoan type ;* as an example of this we may take 

 the base of the singular Gellojpora heterosole, the base, and therefore? 

 the first formed portion of which exhibits Bryozoan characters, 

 while the main mass of the skeleton is of the ordinary Monti- 

 culiporoid type. 



7. Lastly certain extinct forms, the Bryozoan nature of which 

 seems unquestionable, are hardly distinguishable, as regards 

 minute structure, from other forms which have always been 

 regarded as Monticuliporoids. Thus an extremely close 

 structural resemblance obtains between Ceriopora inter jporosa on 

 the one hand and Batoatomella {Montioulipora) tumida on the 

 other. 



WiLi lAM Waagen (Palseontologia Indica, Yol. I, Series XIII, 

 p. 854), has the following to say in regard to the family, Monti- 



*Probably Lindstrom was mistaken in his observations, being deceived by the superimposition of 

 different forms.the incrustation of one form by another being of common occurrence. Two cases 

 of metamorphosis are treated in detail, one of MonticuUpora {Diamulites) petropolitana, which 

 begins as a Ceramopora, and during its growth several times reverts to that form, but M. (D.)peti-o- 

 politana, has unmistakably an intermural gemmation, which would preclude its being a Bryozoan. 

 The other case is still more extraordinary, that of 31. ostiolato. Lindstrom says, that in its earliest 

 stage it is a Discoporella, then a Fistclipora, then a Thecosteoites, finally becoming a Monticuli- 

 PORA. FiSTULiPORA has according to Waagen a coenenchymal gemmation, Thkcosqites a stolonal 

 gemmation and Moxtictjlipora an intermural gemmation. 



72 



