264 Mr. H. J. Carter on the Structure of Stromatopora. 



ccenenchyma may be extended. But this, again, although 

 desirable to notice here, is a point which chiefly belongs to a 

 particularization of the structure in connexion with a descrip- 

 tion of this species. 



Budleigh-Salterton, 

 July 29, 1879. 



EXPLANATION OF PLATE XV. 



Fiy. 1. Stromatopora astroites, Rosen, natural size, showing spots of 

 u stellate venation." (After Rosen, tab. ii. fig. 6.) 



Fiy. 2. Stromatopora, sp. (Pit-Park Quarry, Darlington). Illustrating 

 the rectilinear [structure in a horizontal section of the ccenen- 

 chyma. a, ends of vertical rods, with the rectilinear lines be- 

 tween theru forming the triangular spaces ; b, the same, with 

 the rectilinear lines removed ; c, dark shade to represent the 

 transparent calcite indicative of original hollowness ; d d, ends 

 of rods ; ee, cavity of ccenosarc. 



Fig. 3. The same. Illustrating the rectilinear structure in the vertical 

 section of a little more than a single lamina, a a, the rods ; 

 b b, the horizontal lines limiting the lamina above and below, 

 being produced by the edge of the layer (a, fig. 2) ; c c, inflated 

 ends of the rods uniting respectively with those of the next 

 laminae both above and below; d d, rectangular or quadrilateral 

 spaces, forming part of the ccenosarcal cavity ; the dark shade 

 represents the transparent calcite, indicating original hollow- 

 ness both in the rods and horizontal lines. 



Fiy. 4. Stromatopora, sp. (Pit-Park Quarry, Partington). Illustrating 

 the curvilinear structure in the horizontal section of the ccenen- 

 chyma. a a a a, vemiiculated thread or fibre cut through on the 

 surface ; bbb, vermicular cavities of ccenosarc ; c cc, descending 



f)ortions of vermiculated thread of ccenenchyma. 

 le same. Illustrating the curvilinear structure in the vertical 

 section, a a a, vermiculated thread or fibre cut through verti- 

 cally, showing a tendency to vertical elongation ; bbb, vermi- 

 cular cavities of ccenosarc ; c c cc, descending portions of ver- 

 miculated fibre. 



N.B. Figures 2-5 inclusive are drawn to the scale of about 

 l-9l'ith to l-1800th inch. As the structures vary in size in 

 different species, and, indeed, in different specimens of the same 

 species, so here the rectilinear appears smaller than the curvi- 

 linear, but, from what has been stated, it might have been the 

 reverse. 

 Fiy. G. Stromatopora astroites, Rosen. One star of stellate venation, 

 magnified five diameters. (After Rosen, tab. ii. fig. 7.) The 

 unfinished state of the ultimate branches here is to indicate that 

 they are sunk into the ccenenchyma of the Stromatopora, and, 

 therefore, that the centre is elevated. 



N.B. The fact of the structure of the ccenenchyma being much 

 smaller than the stellate venation is evidenced by fig. 1 (viz. 

 Stromatopora astroites), -wherein the former is too minute to be 

 represented of its natural size, while the latter can be easily 

 seen with the unassisted eye. Hence it must not be expected 

 that the stellate venation can be represented here upon the 

 same scale as the rectilinear and curvilinear structures of the 



