A. E. Verrill — Corals of the Genus Acropora. 225 



not incurved. The wall is covered with elevated thin costula?, which 

 become echinulate lower down, and on the degenerate corallites of 

 the lower side of the branch. 



The coenenchyrna is porous-reticulate, or vermiculate-pitted, and 

 sparingly granulated. 



The Singapore specimens are variously arborescently branched, 

 with rather few divisions, most of the branches not over l6-20 mm 

 thick. The corallites are often few and degenerate on the under 

 side, but generally they are crowded and rather long on the upper 

 side. 



The radial corallites stand at various angles, even on different 

 branches of one specimen. Most commonly they are ascending and 

 stand at 45° to 60°, but they may stand at 90°. They are com- 

 monly nearly terete, tubular, a little tapered, truncate, with the 

 aperture terminal and often only slightly or not at all oblique, but 

 in other cases decidedly oblique, as in the type. The larger ones are 

 often 4-5 mra in length and 2.5 mm wide at base. Between these there 

 are usually many short, verruciform, or subconic corallites. 



All the calicles are very distinctly stellate, usually with 12 septa, 

 the primaries well developed, with wider directives ; the secondaries 

 thin and narrow. The outer wall is generally distinctly thickened, 

 and the outer lip a little prominent and rounded, but not incurved. 

 Externally the wall of most of the calicles is densely covered with 

 minute granulations, generally in longitudinal lines, but sometimes 

 uniformly arranged, giving the surface a smoothish appearance. On 

 the younger calicles distinct costulae are often present, but they are 

 seldom so distinct as in the type. 



The coenenchyrna is also generally very finely and closely echinulo- 

 granulate, like the corallites, but in many parts it becomes pitted, 

 as in the type. 



Some specimens occur in which the corallites of the larger branches 

 and proximal parts of the smaller ones are short-conical or verruci- 

 form, with crowded, swollen bases, unequal in size, and in contact, 

 with small, terminal, stellate calicles, 0.5 mm in diameter. But on the 

 distal parts of the branches corallites of the ordinary form occur. 



This variety has the ccenenchyma and corallites densely echinulo- 

 granulate. It seems to grade into the ordinary varieties, though the 

 small size of the calicles is a striking character. 



At first sight the Singapore variety looks like a distinct species, 

 owing to the fine, dense granulation of the surface, and the longer 

 and more tapered corallites. But some of the specimens have 



Trans. Conn. Acad., Vol. XI. 15 January, 1902. 



