16 



also separate this form from 

 S. granulata, in which the 

 oscula are remote, and can often 

 not be detected at all, though 

 in other respects the surface- 

 characters of the two species 

 are identical. The under sur- 

 face of S. perforata is still un- 

 known ; but the fossil forms 



Fig. 3. a. A fragment of Stromatopora perforata, showing the 

 osculiferous upper surface, natural size ; b. fragment of the same, 

 magnified to show the internal structure ; c. vertical section, 

 bowing the form and course of the canals. 



^V^ = -~=v----' ;r ) faces ; the thicker expansions 



being composed of a succession 

 of crusts superimposed one up- 

 on the other. 



Locality and Formation. 

 Rare in the Corniferous lime- 

 stone of Port Colborne. 



4. STROMATOPORA GRANULATA (Nicholson). 

 Plate I., Figs. 3 and 3 a. 



Stromatopora granulata (Nicholson). Annals and Magazine of Natural History, August, 

 1873, Plate IV., Figs. 3 and 3 a. 



Fossil forming thin crusts, or horizontally-spreading expansions ( usually about a quarter 

 of an inch in thickness, but ranging from one line up to half an inch), often occupying ex- 

 tensive surfaces. Crust composed of concentric calcareous laminae, from six to ten in the space 

 of one line, separated by interspaces which are minutely broken up into cells by numerous 

 delicate vertical rods. Upper surface regularly undulating, often raised into chimney-like or 

 conical elevations, which are for the most part destitute of any appearance of being perforated, 

 but which are sometimes pierced by distinct rounded apertures or " oscula." The entire sur- 

 face is covered with a fine miliary granulation, constituted by minute conical pustules, placed 

 close together, often confluent and arranged in sinuous lines, and apparently imperforate. One 

 example, however, shows that this granulated layer is not the true surface, but that it was 

 covered in the perfect organism by an exceedingly delicate calcareous membrane, perforated 

 with minute apertures or " pores." Exfoliated and broken specimens show that similar gra- 

 nulated surfaces occur at small intervals all through the mass. The under surface (in some 

 cases at any rate, is supported upon a concsntrically-wrmkled calcareous basis, precisely 

 similar to the epitheca of a Favosites or a Fistulipora. 



The specimens upon which I founded my original description (Loc. cit. p. 94) did not 

 exhibit some of the most important of the points comprised in the foregoing specific diagnosis. 

 In none of the examples which at first came under my notice, was I able to detect either 

 oscula or pores. In a fragment, however, of this species, which I discovered in the Hamilton 

 formation of Widder I have now succeeded in detecting both these structures; and I have 

 obtained additional examples from the Corniferous formation, showing the under surface and 

 also the mode of growth, 



S. granulata, is, so far as at present known, one of the few species of Stromatopora in 

 which two sets of apertures exist, one large and exhalant, the other small and inhalant. In 

 the specimen from the Hamilton shales in which these apertures can be detected, the oscula 

 have the form of comparatively large openings, of a circular or oval shape, placed at the sum- 

 mit of distinct rounded or conical elevations. The pores, on the other hand, are only observ- 

 able in a portion of the specimen, and are seen to have the form of minute close-set perfora- 

 tions in a delicate calcareous membrane or layer. Beneath this layer, and over all parts of 

 the fossil where it has been denuded, is seen the ordinary granulated surface from which the 

 name of the species was originally derived. There is thus a strong probability established 

 that all the specimens from the Corniferous limestone, which exhibit simply this granulated 

 surface are imperfect, and that there has been removed from them an exterior and very deli- 



