HISTORICAL INTRODUCTION. 17 



same, viz. G. vesiculosvm and 0. cellulosvm, were briefly defined. The genus 

 Stylodictyon was founded for the singular 8. columnare, Nich., and a second species 

 was included in the genus under the name of 8. retiforme, Nich. and Mur. The 

 latter, however, is really a member of the genus Actinostroma, and is closely 

 related to the A. verrucosum, Goldf., of the European Devonian Rocks. The 

 genus Pachystroma was proposed for certain curious Stromatoporoids of which 

 the new species P. antiquum, from the Niagara Limestone of North America, was 

 taken as' the type. A recent examination, however, of thin sections of the 

 original specimens of Strornatopora concerdrlca, Goldf., has shown that the genus 

 Pachystroma, Nich. and Mur., is nothing more than the veritable Strornatopora, 

 Goldf. (non Strornatopora, auct.), and the name Pachystroma must, therefore, be 

 abandoned. An attempt was made to revive the genus Stromatocerium, Hall, 

 upon the basis of a new species (S. canadense, Nich. and Mur.) from the Trenton 

 Limestone of Canada. Further and more extended observations have shown, 

 however, that this type is really a Labechia in a peculiar condition of preservation. 

 Lastly, the authors accepted the genus Caunopora, Phill., as comprising independent 

 organisms. With regard, finally, to the question of the systematic relationships 

 of the Stromatoporoids, the authors came to the conclusion that, in the absence of 

 any demonstration of the existence in any of the Stromatoporoids of definite 

 zooidal tubes, the reference of these organisms to the Uydrozoa cannot be 

 unconditionally accepted. They concluded, therefore, that with the evidence 

 at that time available, the Stromatoporoids may be best regarded as a separate 

 section of the Calcareous Sponges, for which they proposed the name of Stroma- 

 toporoidea. 



In his ' Petrefaktenkunde Deutschlands' (Schwamme, Pis. 141, 142,1878), 

 Professor Quenstedt treats of the Stromatoporoids among the Sponges. He 

 describes and figures a number of species, mostly from North America ; but it is 

 in most cases difficult to identify the species which he had in view. The species 

 which he names Strornatopora verruculosa seems, as conjectured by Bargatzky, to 

 be really one of the forms included by Goldfuss under the head of 8. polijmorpha, 

 and the form which he terms 8. striatclla, D'Orb., seems to be really the 8. 

 discoidea of Lonsd. (= S. at cyans Rosen) The form described as 8. Worthmi, Rom., 

 is unquestionably identical with that which I described from the Corniferous Lime- 

 stone of Ohio, under the name of Stylodictyon (Si/ringostroma) col urn wire. 1 The 

 form named Strornatopora, ccespitosa is the Idiostroma ccespitosum of Winchell, 

 and should be placed in Idiostroma. The other forms described are Strornatopora 

 textilis, Rom., 8. minuta, Winch., S. pnstulifera, Winch., and S. consors, Quenst., 

 all from the Silurian and Devonian Rocks of North America. 



1 I Lave not been able to discover that any description of this species has been published by 

 Eominger. 



