10 Dr. 11. A. Nicholson on the Genus Stromatopora. 



taincd in the genus Stromatojyora. My own opinion is de- 

 cidedly against forming a new genus for its reception, since 

 it has the essential structure of Stromatopora ; and the difficulty 

 which I experienced at first in detecting the oscula, even in 

 the examination of a large series of specimens, has convinced 

 me that the occurrence of similar openings may well have been 

 overlooked, even in the type species of the genus. 



2. Stromatopora granulata, Nicholson. 



Stro?natopora granulata, Nicholson, Ann. & Mag. Nat. Hist., Aug. 1873, 

 pi. iv. figs. 3, 3 a. 



The specimens upon which my original description of this 

 species {loc. cit. p. 94) was founded were all from the Corni- 

 ferous Limestone ; and I failed to detect in them any traces 

 of apertures which could be regarded as either pores or oscula. 

 Recently, however, T have obtained an example of S. granu- 

 lata from the Hamilton group of the township of Bosanquet, 

 showing both these sets of apertures ; and I have also obtained 

 additional specimens from tlie Corniferous Limestone shoAving 

 the under surface and the mode of growth. 



The first of the above-mentioned specimens is only a frag- 

 ment ; and its greater portion exhibits all the appearances 

 which characterize the Corniferous examples of the species. 

 The upper surface of the fossil exhibits several rounded or 

 conical elevations, one of which is perforated by a large sub- 

 circular apertm'C leading down into the interior, and evidently 

 of the nature of an osculum. Whether the other elevations 

 were similarly perforated or not does not clearly appear. The 

 pores are only shown over a small portion of the fossil, and 

 have the form of minute close-set perforations in a delicate 

 calcareous membrane or sui^f ace-layer. Beneath this layer, and 

 over all parts of the specimen whence it has been denuded, is 

 seen the ordinary granulated surface fi-om which the name of 

 the species was originally derived. There is thus a probability 

 established that all the specimens from the Corniferous Lime- 

 stone which exhibit simply this granulated surface are imper- 

 fect, and that there has been removed from them an exterior 

 and very delicate membrane in which the pores were pierced. 

 The granulated layer which appears to form the sm-face in so 

 many specimens would seem on this view to have served the 

 pur})Ose of distributing the water received through the external 

 poriferous layer, the granules witli which it is studded being 

 more or less confluent, and giving rise to a complicated system 

 of sinuous or vermicular horizontal channels. 



The under surface of S. r/ranulata is covered by a tliin, con- 



