PROBLEM OF THE MONTICULIPOROIDEA 23 



AFFINITIES OF TREPOSTOMATA 



Regarding the affinities of the Monticuliporoidea as a whole, 

 the evidence uniting these to the Bryozoa on the one side, and 

 to Tabulata or Alcyonarian corals on the other, does not lead to 

 a compromise conclusion that they really were related to both as 

 an intermediate or connecting link, because, as will be seen, the 

 interpretation of the zoarium necessary to unite them with the 

 one is discordant to that necessary to unite them with the other; 

 and because of evidence to the contrary from the embryology 

 of living Bryozoons and corals. Discussion is therefore confined 

 to the question whether the extinct Monticuliporoidea are 

 Bryozoa or Coelenterata. 



In relation to Bryozoa, the problem begins with the Treposto- 

 mata section, some or all of which have been variously and 

 doubtfully referred to Cyclostomata ; and this order of Bryozoa 

 is extant. The reference involves comparison with the sup- 

 posed Cyclostomatous genera Neuropora and Heteropora, of which 

 we are yet uncertain. Gregory 1 refers these as typical Treposto- 

 mata, not Cyclostomata. The question rests mainly upon the 

 fossil and recent Heteropora which Nicholson 2 has thoroughly 

 discussed and which, as it appears, simulates Trepostomata, but 

 has many transverse mural pores and other differences. Tre- 

 postomata must therefore be proved to be Bryozoa and Hetero- 

 pora likewise to belong to Trepostomata, before they can be 

 united with assurance. Gregory's reference needs proof and 

 affords no evidence, but expresses well perhaps that we are uncer- 

 tain of all. Passing to the comparison of Trepostomata with 

 undoubted Bryozoa, this requires knowledge of the extinct 

 Cryptostomata, which must in turn be compared with Bryozoa; 

 and discussion of that part of the problem will therefore be 

 deferred to the section on Cryptostomata. 



In relation to Tabulata or Alcyonarian corals, Trepostomata 

 may be compared immediately. In the first place, such forms 

 as Monotrypa compare with Chcztetes, a massive zoarium of small, 



'Catalogue of Jurassic Bryozoa, p. 193, 1896. 



2 Structure and Affinities of the Genus Monticulipora, p. 62. 



