A. E. Verrill — Corals of the Genus Acropora. 223 



lites are mostly strong]}" appressed and imbricated, seldom arranged 

 serially, but rather in quincunx. The more distal ones are some- 

 what spreading, mostly compressed, tubo-nariform, the larger ones 

 4-5 mm long, 1.5 mm broad, with the aperture very oblique and ellipti- 

 cal; the inner lip may be wanting, or short and thin; the outer lip 

 is elongated, a little thickened, either obtusely rounded or narrowed, 

 usually a little incurved, both lateralty and distally. The radial 

 corallites, a little lower down, gradually become more appressed, 

 with the outer lip narrower and more pointed, and the inner lip 

 abortive. The wall of the distal corallites is strongly grooved and 

 costulate, with sharp-edged and finely echinulate costulae; those lower 

 down have less prominent costuloe, and larger, rough or sharp gran- 

 ules in series ; the lower lip is perforate between the costulse. 

 Toward the base of the branchlets the corallites become much 

 shorter, closely appressed, but still tubular, with nearly round calicles. 

 On the larger basal branches there are many immersed calicles, with 

 a very distinct 12-rayed star, and many others with a slightly raised 

 border. These calicles are very distinctly stellate with six wide and 

 six narrow septa, and are 0.75 to O.S mm in diameter. 



All the radial calicles have six strong primary septa, the directives 

 wider, and six narrow secondary ones. 



The coenenchyma is firm, but porous, and roughly echinulate, 

 with rather large, sharp granules, often in series. 



The specimens from Singapore agree well with the types in the 

 size and form of the branches and corallites, but the walls of the 

 corallites often lack the costuhe and are densely covered with fine 

 sharp granules, which may be in series ; but in most cases the distal 

 and less appressed corallites are more or less costulate, even when 

 those below are evenly echinulate. In some of these specimens the 

 outer lip of the larger radial corallites is thicker and more convex, 

 so that the form is slightly scaphoid. 



But in the large series of specimens examined, there are all inter- 

 mediate states and many other variations. 



Hence I am led to doubt the distinctness of A. appressa (Ehr.) ; 

 A. assimilis (Br.); and A. alliomorpha (Brook), all of which are cer- 

 tainly much alike. 



Brook, himself, refers Dana's appressa to his assimilis, but the 

 general figure of the latter (from a photograph) shows some differ- 

 ences. The most notable is the very evident arrangement of the 

 corallites in vertical series, which I have not observed to any marked 

 extent in the Singapore specimens. The type photographed by him 



