﻿ULRICH BASSLER] REVISION OF PALEOZOIC BRYOZOA '9 



forms that do nol agree strictly with the genotype; and when it was 

 found that these doubtful species formed a reasonably distinct and 

 apparently genetically related group, it seemed no more than serving 

 the best interests of classification to apply a new generic term. This 

 new genus for which we propose the name Orbignyella, in honor of 

 the author of Monticulipora, is distinguished from tin- latter genus 

 in wanting its peculiar, irregularly granulose wall structure, in 

 having less clearly defined cystiphragms, these structures appearing 

 more like merely curved diaphragms, and in possessing more or less 

 well developed and sharply defined true acanthopores. The wall 

 structure of this new genus is more like that prevailing among the 

 Heterotrypidce than the Monticidiporidce, and it is only on account 

 of curved diaphragms that we place Orbignyella with the latter 

 family. At best the reference is doubtful, and the ultimate position 

 of the genus, which should depend upon its genetic relations, may be 

 quite different. 



The following new species, O. sublamellosa, from the Stones River 

 formation of Tennessee, being the most abundant form showing all 

 the generic characters, we have adopted as the genotype. Of de- 

 scribed species, Monticulipora wetherbyi and .1/. lamellosa Ulrich, 

 of the Ordovician, are referred here with certainty, while Chcetetes 

 cxpansus Ringueberg, of the Rochester shale and Monticulipora 

 billingsi Foord are doubtful members. Four or five additional, but 

 as yet undescribed, Ordovician species are known. 



Certain Devonian species now referred to Monticulipora, of which 

 M. winchelli Ulrich is a good example, may possibly belong to 

 Orbignyella, but we prefer for the present to leave them where they 

 are, despite our conviction that they are generically distinct from 

 Monticulipora. In common with practically all the known Devonian 

 Trepostomata they have certain peculiarities that are as yet little 

 understood and that require a special investigation before it may be 

 deemed wise to reclassify the species. 



ORBIGNYELLA SUBLAMELLOSA new species 



(Plate VI, 7-9) 



Zoarium of wide lamellate expansions formed of superposed layers 

 varying from 3 to 10 mm. in thickness ; subcorneal masses sometimes 

 result from the continued piling up of these layers. Maculae not 

 elevated but conspicuous because they are composed of aggregations 

 of mesopores and zocecia of larger size than the average. Zocecial 

 apertures small, thin-walled, 8 to 9 in 2 mm. Acanthopores small 



