A. E. Verrill — Corals of the Genus Acropora. 221 



from a specimen supposed to be one of Lamarck's types. But it was 

 probably included under that heterogeneous species by Lamarck and 

 by Edw. and Haime. 



This species forms broad convex clumps of rather stout, upright, 

 more or less divided, obtuse branches, with a large, swollen axial 

 corallite. The clumps arise from a broad, short basal mass ; the 

 outer and under ones are curved and spread out nearly horizontally 

 in the larger specimens, and they often become flattened, irregular, 

 and more or less coalescent, but they may be much coalescent on one 

 side of a clump and entirely free on the other. In young specimens 

 the outer branches are less spreading, or more upright, and do not 

 coalesce. The central branches of the upper side are mostly 60 to 

 70 mm long, often forked at the base, and may give off two or more 

 small divergent, ascending branches from the middle portion, or dis- 

 tally. The calicles of the horizontal branches and bases of the 

 upright ones are mostly immersed, but rather large and conspicuous, 

 with a very distinct star of six primary septa, the directives larger. 

 Our largest specimen (No. 6118, from Singapore) is a foot in diame- 

 ter (300 mm ), and half as high. I have seen others considerably 

 larger, from Singapore. 



The axial corallites are large (4 mm ), very short, obtuse, with very 

 thick, openly porous walls, and a rather small calicle (l mm ), which 

 has a distinct star of 12 septa, the directives wider. The lateral 

 calicles are various in size and form. The larger ones are large and 

 thick, tubular, strongly ascending, but not much appressed, with the 

 distal margin obliquely truncate, so that the margin of the calicle is 

 very oblique. 



The outer side of these calicles is much thickened and rounded at 

 the outer lip, so that the corallites often appear slightly scaphoid ; 

 in some cases they are somewhat appressed, but usually the inner lip 

 is fairly well developed, though much shorter and thinner than the 

 outer. The star is very distinct, usually with 12 septa; the six 

 primaries are wide, the directives broader ; those of the second cycle 

 are very narrow and thin, often absent. The exterior wall of these 

 corallites is porous and densely echinulate-costate, the small spinules 

 being arranged in costal lines. 



Among the larger corallites are many others that are equally wide, 

 but much shorter, more divergent, the calicles opening more out- 

 ward, 'but with a similar thick outer lip and star. Lower down 

 many are verruciform and a few small ones are immersed. 



The coenenchyma of the branches is firm, but somewhat porous, 



