24 BRITISH STROMATOPOROIDS. 



In the ' Twelfth Report on the Geology of Indiana,' 1882, p. 263, Prof. Hall 

 figures a Stromatoporoid, which he considers as probably identical with 

 Syringostroma densnm, Nich. 



In 1881, 1882, and 1883, Monsieur E. Dupont published three successive 

 papers on the structure of the Devonian and Carboniferous Limestones of Belgium, 

 viz. (1) " Sur l'Origine des Calcaires Devoniens de la Belgique," 1881 ; (2) " Les 

 lies Coralliennes de Roly et de Philippeville," ' Bull, du Musee Royal d'Hist. Nat., 

 t. i, 1882 ;' and (3) " Sur les Origines du Calcaire Carbonifere de la Belgique," 

 1883. In these papers the author draws attention to the very important part 

 played by the Stromatoporoids in the formation of the Devonian Limestones of 

 Belgium, and concludes that these organisms commonly constituted reefs of a 

 similar nature to the coral reefs of the present day. M. Dupont is also of opinion 

 that certain of the Carboniferous Limestones of Belgium (e. g. the Limestone of 

 Waulsort) are composed of organisms related to the Stromatoporoids. For these 

 organisms, or for certain of them, the author proposes the generic names of 

 Stromatactis , Stromatocus, and Ptylostroma ; but the distinguishing characters of 

 these genera are not given. M. Dupont has been so good as to furnish me with 

 specimens of Stromatactis, but I have not been able to recognise in these any 

 characters which would lead me to suppose that they could be placed in the group 

 of the Stromatoporoids. 



In 1882, Mr. S. A. Miller described a Stromatoporoid from the Cincinnati group 

 under the name of Stromatocerium richmondense (' Journ. Cincinnati Soc. Nat. 

 Hist.,' vol. v). This paper I have not seen. 



In 1883, Prof. Ferdinand Roemer published the second part of the text of his 

 great work, the ' Letha^a Palseozoica,' the plates for this having appeared in 1876. 

 In this work the Stromatoporoids are placed among the Hydrozoa, and an account 

 of their general characters and structure is given. The author maintains most of 

 the distinctive views which he had previously published with regard to these 

 organisms. He regards the surface as invariably destitute of larger apertures of 

 every kind, which is certainly not the case in various species in which " astro- 

 rhizae" are well developed, many such having well-marked openings in the centre 

 of the astrorhizas. The composition of the horizontal " lamina?," out of horizontal 

 anastomosing processes, which leave minute openings between them, is also not 

 recognised by the author, though readily capable of demonstration in well- 

 preserved examples. The " radial pillars " are looked upon as being invariably 

 solid — a view which has been generally held, but which is certainly by no means 

 always correct. The lower surface is rightly stated to be usually covered by a 

 thin, concentrically-wrinkled epithecal membrane, and not to be cemented down 

 to some foreign body. The " astrorhiza?" are regarded, erroneously, as having no 

 value as a specific character, and the absence of central vertical canals is asserted, 



