HISTORICAL INTRODUCTION. 21 



On the other hand, as I shall point out more fully later on, this explanation by no 

 means applies to such openings as are observable in Stromatopora ? polyostiolata, 

 Barg., Stromatoporella granulata, Nich., and various other types, in which rounded 

 apertures are seen to be regularly disposed over the surface, and often to be sup- 

 ported upon prominent " mamelons." In these cases, the superficial openings 

 belong in the strictest sense to the structure of the Stromatoporoids themselves, as 

 can conclusively be shown by the fact that thin vertical sections demonstrate them 

 to be the mouths of approximately vertical, wall-less tubes, which form the axes of 

 successively superimposed groups of " astrorhizse." 



In 1880, Mr. Carter published a paper ('Ann. and Mag. Nat. Hist.,' ser. 5, 

 vol. vi, p. 339) in which he criticised the memoir just mentioned. Contrary to 

 the views of Roemer, he expressed the opinion that the tubes of Caunopora can 

 not be ascribed to Aulopora repens, as an invariable rule at any rate, as they some- 

 times possess infundibuliform tabulae, resembling the tabulae of Syringopora. 

 Much stress, however, cannot really be laid upon this argument, as undoubted 

 species of Aulopora can be shown to sometimes possess funnel-shaped tabulae. In 

 the same paper, Mr. Carter proposes the convenient name of " astrorhizae," for 

 the stellate ccenosarcal canals of certain of the Stromatoporoids ; and he describes 

 a Stromatoporoid from Devonshire, under the name of Stromatopora dartingto- 

 nensis, in which he has detected transverse plates, resembling " tabulae," in the 

 branches of the astrorhizae. As to the occurrence of these transverse calcareous 

 partitions in the branches of the astrorhizae, no doubt whatever is possible. I am, 

 however, unable to accept Mr. Carter's conclusion that these structures are in any 

 way comparable with the "tabulae" in the tubes of the " gastrozooids " of Mille- 

 j)ora, a view which he further maintains in the present memoir. For one thing, 

 many Stromatoporoids (such as the 8 'tromatoporidoi generally) really do possess other 

 structures comparable with the " tabulae " of Millepora. Moreover, to accept this 

 view would, as it seems to me, entirely upset the much more reasonable comparison 

 of the "astrorhizae" of the Stromatoporoids to the branched coenosarcal grooves 

 of Hydractinia and to the irregularly-divided canal-system of the general skeleton 

 of MiUepora — a comparison which has been ably supported by Mr. Carter himself. 



In the 'Neues Jahrbuch fur Mineralogie,' &c. (Jahrg. 1880, Bd. ii, p. 403), 

 Dr. Steinmann reviews Mr. Carter's previously noted paper on Caunopora. He 

 expresses the opinion that Ferd. Roemer and Carter are correct in their conclu- 

 sion that the genus Caunopora is founded upon specimens in which a Stromato- 

 poroid and a Coral are associated as commensals. 



The principal work dealing with the Stromatoporoids, which appeared in the 

 year 1881, is the elaborate memoir by Dr. August Bargatzky on the Stromato- 

 poroids of the Rhenish Devonian formation (' Die Stromatoporen des rheinischen 

 Devons,' Bonn, 1881). I shall have occasion to frequently refer to this memoir, 



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