190 PEOr. H. A. NICHOLSON AND DR. J. MUKIE ON THE 



Limestone of North America, the structural characters of the 

 genus, however, being left undefined. In the same work (vol. ii. 

 p. 135, 1852) Prof. Hall states that, according to his observations, 

 the skeleton of Stromatopora is " composed of minute cylindrical 

 tubes with considerable space between, and that the laminated 

 structure arises from thin layers of calcareous matter deposited 

 and filling the spaces between and filling the tubes." He consi- 

 ders the genus to be referable to the Corals, and to be " more 

 nearly related to Tuhifora than to any other genus." 



In the 'Prodrome de Paleontologie ' (1850), D'Orbigny places 

 the genus Stromatopora among the Sponges, and gives short de- 

 finitions of some species, founded, of course, upon macroscopic 

 characters only. In the ' Cours Elementaire de Paleontologie ' 

 (1851), the same observer again places the genus in the same syste- 

 matic position. D'Orbigny's genus Sparsispongia, however, would 

 seem to be founded upon Stromatoporoids of the type of, or 

 identical with, Stromatopora polymorpha^ Groldf. 



In 1851, Prof. M'Coy Brit. Pal. Foss.' p. 12) expressed the 

 opinion that Stromatopora is a true Coral, allied to Mstulipora and 

 Pal(Eopo7'a {=HeUoUtes'). His definition of the genus is : — "Co- 

 rallum calcareous, forming large amorphous masses composed of 

 very thin superposed layers of minute vesicular tissue of the 

 thickness of one cell each, occasionally marked on the upper sur- 

 face with extremely obscure, distant, quincuncially-arranged small 

 pits." 



The two Sandbergers (' Die Versteinerungen des rheinischen 

 Schichtensystems in Nassau,' 1850-56, p. 380) consider that ^^ro- 

 matopora properly belongs to the Polyzoa ; but they base this view 

 upon the unquestionably erroneous interpretation of the " radial 

 pillars " as being tubes. 



The same view as to the affinities of Stromatopora is expressed 

 by Professor Ferdinand Eoemer (' Lethaea Geognostica,' 3rd ed. 

 vol. i. p. 166), who compares the genus with the recent Celle- 

 pora ; and who explains the apparent absence of " cells " upon the 

 ground that perhaps these structures were extremely minute, or 

 the cell-walls were very destructible. Eoemer adds, however, 

 that since he expressed this opinion, he has examined specimens 

 of aS. polymorpha from the Eifel, in which he can detect both 

 prismatic tubes and tabulae, and that the genus will therefore pro- 

 bably have to be removed to the " Tabulate Corals " and placed 

 near Chcetetes and Favosites. 



