96 TABULATE CORALS. 



surfaces as well as on the edges of the corallum. In spite, 

 however, of this close general resemblance, I do not yet feel 

 absolutely satisfied that the present species is rightly referred 

 to the genus Pachypora, Lindst. ; and it will require more ex- 

 tended investigations than I have hitherto been able to carry 

 out before this point can be finally settled. In fact, P. frondosa 

 exhibits a union of the features which characterise PachypoTa 

 proper with those distinctive of Coenites, and I am not sure' 

 that it will not be ultimately necessary to remove it to the 

 latter genus. This point is especially shown by the calices. 

 These openings, though never actually rounded or polygonal, 

 are often oval, and they are seen in sections parallel with the 

 surface (fig. 1 7, c) to be surrounded by a dense deposit of 

 sclerenchyma, as in Pachypora. On the other hand, the calices 

 are commonly subtriangular, and in parts of the frond they are 

 generally quite crescentic or even fissure-like, while the lower 

 lip is sharp and thin, and may project inwards as a single or 

 double tooth, as in Cceiiitcs. Moreover, though the walls of 

 the corallites are thickened, and the calices thus rendered re- 

 mote, I have failed to detect the delicate concentric laminae of 

 sclerenchyma so characteristic of Pachypora ; and the walls of 

 contiguous tubes are completely incorporated, and exhibit no 

 clear line indicating their original separateness. The com- 

 paratively numerous septal spines of P. lamcllicornis, Lindst., 

 are here wanting, but one or two ridges on the interior of one 

 of the walls of the corallites may represent septa. In other 

 cases, however, the tubes appear in transverse section (fig. 

 1 7, c) to be oval or rounded, and there may be no traces of 

 septal ridges or tubercles. Thin sections taken along the 

 median plane of the expansion, and cutting the tubes longi- 

 tudinally (fig. I 7, d), show no signs of tabula;, or but unsatis- 

 factory ones ; but sections taken at right angles to the flat 

 surfaces of the frond (fig. 1 7, e) show that these structures are 

 at any rate occasionally present, when they are few, remote, and 

 complete. I have not been able to discover mural pores other- 

 wise than by the presence of lateral communications between 



