14 Dr. II. A. Nicholson o?} the Genus Stromatopora. 



produced by their intersection witli the interlaminar spaces. 

 Lastly, the general surface is undulating, and the oscula are 

 not elevated upon eminences or papillae. 



This remarkable species departs in some important respects 

 from the structure of the typical species of Stromatopora ; but 

 it presents at the same time such a close resemblance to forms 

 like >S'. tuherculata that it docs not seem necessary to form a 

 new genus for its reception. The chief peculiarity of the pre- 

 sent form depends upon the fact that the component laminjB 

 of the mass are not arranged concentrically as regards the 

 entire mass ; but the fossil is composed of concentric layers, 

 each of which is composed of parallel or subparallel lamina? 

 disposed obliquely to the surfaces of the stratum. Hence tlie 

 interlaminar spaces, instead of being parallel with the surface 

 of the mass (as in S. tuherculata and 6'. granulatd)^ open upon 

 the surface in the form of oblique, sinuous, or vermicular open- 

 ings, sometimes rounded or subtriangular, but more commonly 

 linear and having a transverse diameter of about one hundredth 

 of an inch. It can hardly be doubted that these minute open- 

 ings, which cover the greater part of the entire surface, are of 

 the nature of inhalant apertures or "pores;" and they com- 

 municate to fragments of this fossil very much the aspect of 

 worn and weathered examples of certain forms of Alveolites 

 and Coenites. All those portions of the surface which are not 

 occupied by the pores are taken up by very much larger open- 

 ings, which are certainly exhalant apertures or " oscula." 

 Very often the lamina? are arranged in any given stratum in 

 a subspiral manner round certain points of the mass, and the 

 pores on the surface have a corresponding arrangement. 



Upon the Avhole, little doubt can be entertained as to the 

 propriety of referring this species to the Calcispongias ; and 

 its structure would strongly corroborate the view that the 

 surface-tubercles in S. tuherculata are truly perforated, and are 

 of the nature of pores, though examples of this species as 

 ordinarily preserved do not exhibit this feature clearly. I 

 have named the present species after its discoverer, Mr. George 

 Jennings Hinde, who has kindly furnished me with specimens 

 for examination. 



Locality and Forviation. — Common in a magnesian lime- 

 stone of the age of the Niagara Limestone (Upper Silurian), 

 at Owen Sound, Ontario. Collected by Mr. G. J. Hinde. 



