NIAGARA GROUP. 



147 



I have referred this species to Callopora, from its possessing the essential characteristics of 

 the preceding, differing perhaps in the character of the intercellular spaces, which appear to 

 be solid upon the upper surface. The apertures of the cells are smaller, and often only tri- 

 petaloid or formed by segments of three or four curves. The coral is, to the naked eye, 

 apparently quite solid, but the minute cylindrical tubes penetrating the mass are very distinct 

 under a magnifier. The spaces between the tubes, though appearing to be of uniform texture, 

 still show, when highly magnified, the lines of the transverse septa, giving a kind of cellular 

 appearance to the mass. The structure and mode of growth do not, therefore, differ in any 

 degree from the preceding species. 



There is no appearance of the minute spinulose or papillose points around the aperture which 

 occur in the preceding and following species, but it is possible that these have been removed 

 by abrasion, which has likewise obliterated the marks of intercellular tubes ; still the surface 

 gives no evidence of having been worn. This coral, from its apparent structure, could be re- 

 ferred to Stromatopora, without doing violence to the essential characters of that genus. 



Fig. 3 a. The surface showing the openings of the natural size. 



Fig. 3 i. A section showing its mode of growth in concentric laminae. 



Fig. 3 c. The lower surface, showing the concentric striated membranous covering. 



Fig. 3 (i. A portion of the surface enlarged, showing the form of the mouths of the cells. 



Fig. 3 e. A section enlarged, showing the vertical tubular cells and transverse septa. 



Position and locality. In the shale of the Niagara group at Lockport. 



537. 4. CALLOPORA ASPERA (71. ^/).). 



Pl. XL. Fig. 4 o - i. 



Coral growing in solid or hollow cylindrical stems, often incrusting other bodies in broad 

 explanate or foliate expansions ; stems usually thickened or clavate at their extremities ; cells 

 tubular, openings circular or slightly oval, with finely reticulate interspaces ; margins of the 

 aperture surrounded by minute points, which give the entire surface an asperato-granular 

 appearance ; vertical section tubular or columnar ; intercellular spaces septate ; the form of 

 apertures and intermediate spaces often very irregular towards the margin of an incrusting mass. 



In unworn specimens, the minute points surrounding the apertures of the cells give a very 

 peculiar and characteristic appearance to the surface. The apertures are smaller and of different 

 form, and the intermediate spaces more finely reticulate than in the two first species ; and in 

 worn specimens the appearance and texture is more delicate, though it assumes a greater 

 variety of appearance than either of the preceding species. In its growth it often surrounds 

 the stems of crinoids, probably while the latter are in a li^-ing state ; in other instances the 

 centre of the stem is filled with amorphous mineral matter, while the coral forms an en- 

 veloping hollow cylinder. This feature may arise from the mode of growth, the coral first 

 enveloping the stem of a crinoid, and afterwards growing on beyond its extremity while the 



