species of Stromatopora. 91 



liarities which, so far as I am aware, are altogether unique. 



In the first place, it is not composed, as are S. striatella, 

 D'Orb., and S. concentrica^ Goldf. (which it most nearly re- 

 sembles in general form), of a succession of laminae concen- 

 trically arranged round an imaginary centre or centres. On 

 the contrary, in the present species, intercalated amongst the 

 general enveloping concentric laminae of the mass is a series 

 of cylindrical masses, each composed of laminse concentric 

 with its long axis, and each terminating (probably at both 

 ends, though this is not shown; in a rounded nipple-shaped 

 extremity. Superiorly these laminated cylinders are enveloped 

 by laminffi which are concentric to the whole mass, so that the 

 outermost surface is simply undulating. On two of the sides 

 of the fossil the ends of the above-mentioned cylinders protrude 

 as so many nipple-shaped conical prominences, giving these 

 aspects of the mass very much the appearance of the pecidiar 

 inorganic structure known as "cone-in-cone." 



In the second place, a still more remarkable feature is pre- 

 sented by the upper surface of the fossil. The specimens are 

 so highly mineralized (as is always the case with the fossils of 

 the dolomites of the Guelph formation) that the smooth un- 

 dulating upper surfaces of the laminge exhibit no structure that 

 can be made out with the lens. If any pores existed, as is 

 most probable, they cannot now be detected. The upper 

 surface, however, exhibits tolerably regular diagonal lines of 

 small conical papillae, some of which at any rate are unmis- 

 takably perforated by rounded apertures. It is true that some 

 of these eminences do not show any sign of being perforated ; 

 but this is probably, indeed almost certainly, due to the peculiar 

 condition of mineralization of the fossil. The perforated 

 eminences are distant from two to four lines from one another ; 

 and the diagonal rows stand about as far apart. The appear- 

 ance presented by the upper surface, with its perforated papillae, 

 thus comes to simulate somewhat the root of a fossil plant like 

 Sttgmarm, with the points whence the rootlets proceeded. 

 The eminences themselves are but slightly elevated above the 

 general surface ; and the apical aperture has a diameter of about 

 one thirtieth of an inch. Not only does the outermost or 

 highest lamina of the fossil exhibit the above appearance, but 

 the same structure reappears at intervals of two to three lines 

 all through the mass, each surface being concentric with the 

 preceding one, and separated from it by reticulated tissue. It 

 is probable, therefore, that we should regard the fossil as really 

 consisting of thin crusts, which are only accidentally super- 

 imposed one above the other. 



