A. E. Verrill — Corals of the Genius Acropora. 229 



■the two directives. The outer wall is covered witli imiDerous, very 

 thin costulte. 



The more distal corallites are a little more ascendiin^-, but the 

 lower lip is slightly excurved and expanded, so that the calicles are 

 conspicuous. Some smaller immersed calicles (C.G""" in diameter) 

 are found between the labiate ones nearly to the tips of the branches. 



The axial corallites are moderately large (2.5 to 3™™), with thick 

 walls, and onl}^ a little exsert. The axial calicle is small (1"""), with 

 12 subequal, thin, but not narrow, septa. 



The coenenchj'ma of the branches is rather dense, with few small 

 pores, and its surface is covered with rather coarse, rough or sharp 

 spinules, not crowded, and mostly arranged in longitudinal series, or 

 often united into irregular costulae or small tabulae. 



The origin of the type is unknown, but is doubtless Indo-Pacific. 



Acropora effusa (Dana) Ver. See p. 215. 



Madrepora effusa Dana, Zooph., p. 455, 1846. Brook, p. 76 (non Quelch). 



Plate XXXVI. Figures 16, 16a. Plate XXXVI B. Figures 7, 7«. 



Dana's unique type of this sjsecies from Ceylon (coll. Rev. Geo. 

 H. Apthorp) is in the Museum of Yale University. 



It is a regular corymbose clump, with a slightly convex surface, 

 10 by 14 inches (250X350'"'") across, and 5 inches (125'"'") high. 

 The upper surface is covered with upright branches 25 to 40""" long, 

 arising from a solid basal mass of coenenchyma, covered above with 

 immersed stellate calicles. The base is broadly incrusting, about 

 250°^"^ across, and free marginally only for a slight distance, except 

 on one side, where the free part is 75 to 100""" wide. It here forms 

 a nearly solid plate of coalesced branches, with a few submarginal 

 openings, without free branchlets, but covered thickly with exsert, 

 conoidal, verrucose, and tubular corallites, 1-.3'"™ long, with porous, 

 echinulate walls and -rayed, stellate calicles, the directives wider. 

 There are few immersed calicles beneath. The coenenchyma of the 

 outside base is very porous. 



The marginal branches are nearly horizontal at l>ase, and coales- 

 cent ; submarginal ones are curved upward distalh^ ; those nearer 

 the middle are straight, upright, parti}' simple and partly forked, or 

 more or less proliferous; they are rather stout and tapered, 10 to 

 15'"'" thick at base, subacute, with a moderately large, but not swol- 

 len, axial corallite, 2.5-3.5"^™ in diameter, and l-:5'"'" exsert, with 

 rather thick, openly porous, costulate walls. 



