BKYOZOA. 313 



sections), as reasonably conclusive. But if the peculiar granu- 

 lar structure of the walls of these Bryozoa is admitted to be 

 conclusive evidence of their originally porous condition, we must 

 also admit that the walls of Monticulipora (restricted) and the 

 CERAMOPORID.E were porous as well, since thin sections of those 

 forms exhibit precisely the same granular wall structure. The 

 same also applies to many FISTULIPORHLE. 



Nicholson and Ethridge jun. claim to have discovered "mural 

 pores'' in species of Stenopora*. Unfortunately for the discovery 

 the very illustrations which these observers give to show these 

 structures, also show in on unmistable manner that the dis- 

 covery is founded upon faulty observation. Their new species 

 S. jackii is said to exhibit the "mural pores" in a more satis- 

 factory manner than any of the others studied by them. Three 

 figures are given, two of them (b, c) enlargements of a, repre- 

 senting a vertically split branch. The explanations to the 

 figures set forth that b and c show the annulations of the tubes 

 in their outer portions and the mural pores. A knowledge of 

 the minute structure of Stenopora,, such as we must believe these 

 authors possessed, should immediately have explained certain 

 peculiarities which are presented by the specimen figured. The 

 authors ought furthermore to have seen that the form of the 

 tubes ascribed by them to S. jackii is totally different from 

 that of ovata, Lonsdale, in being brought into contact with 

 each other only at subregular intervals by periodic ring-like 

 swellings, instead of being in contact throughout their length. 

 On the other hand, a little more careful examination would, 

 perhaps, have revealed the fact that the interspaces between the 

 supposed tubes correspond exactly with the walls of a Steno- 

 poroid as they appear in vertical sections. The fact of the 

 matter is that these usually so cautious observers were mislead 

 bj* a peculiar, yet not uncommon state of preservation, con- 

 sisting, namely, of the dissolving or wearing away of the actual 

 walls of the zoarium, whereby the siliceous or semi-siliceous 

 casts of the interior of the tubes is exposed to view. Specimens 

 of S. carbonaria Worthen, from the Coal Measures of Illinois, 



*Ann. & Mag. Nat. Hist. 1879, VoL IV, p. 275. 



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