PROBLEM OF THE MONTICULIPOROIDEA. II 



CRYPTOSTOMATA 



Cryptostomata are quite generally classed as Bryozoa, but 

 their reference as such can still be treated as doubtful. They 

 occupy, in fact, a central position in the disputed field of Paleozoic 

 tabulate fossils. They are quite inseparable from Trepostomata 

 which are most often classed as Ccelenterata. To prove them 

 undoubtedly Bryozoa is to prove Trepostomata such also. To 

 fail in that proof permits the latter to be classed as Tabulata, 

 true Ccelenterata, and the Cryptostomata should then be carried 

 with them. 



Four similar groups of tabulate corals and bryozoons appear 

 for their first geologic occurrence in the Ordovician (Lower 

 Silurian). The Tabulata, or Alcyonarian corals, are there repre- 

 sented by a few but typical species, the Trepostomata are locally 

 in great numbers, and with them are many Cryptostomata and 

 a few Cyclostomata, the last being true Bryozoa. To the top 

 of the Paleozoic these four groups remain associated, but there 

 the Cryptostomata become extinct. Only in middle Mesozoic 

 the fifth group, comprising the Chilostomata to which most living 

 Bryozoa belong, appears at a time when even the Trepostomata 

 have quite disappeared. The fifth and last group seems to come 

 in suddenly, as did the others. Evidently the record is incomplete 

 as to their origin, and the missing evidence has therefore to be 

 supplied. Some Cryptostomata resemble in all ways the Tre- 

 postomata and these the Tabulata ; others somewhat nearly 

 simulate the Cyclostomata ; and again it has been suggested 1 

 that they " are nothing more than Paleozoic Chilostomata," dif- 

 fering from these, however, in several ways. The problem 

 centers about the Cryptostomata. 



Besides this interest which the problem of phylogenic rela- 

 tionship affords to the paleontologist, the geologist finds, or can 



1 See Eastman, Text-book of Palaeontology, p. 278. 



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