A. E. Verrill — Corals of the Genus Acropora. 209 



metrical and usually larger axial corallite at the enil of each braucli 

 (sometimes more than one), which produces radial or lateral buds 

 around its base. These buds mostly develop into a symmetrical, 

 often one-sided or labiate radial corallites in which the zooids may 

 have longer directive tentacles and wider directive septa. 



More or less of the radial corallites become larger and symmetri- 

 cal and eventually may become the axial corallites of new branches 

 or branchlets. 



Other radial corallites, Avithout prominent lips, often occur on the 

 larger branches, or on their under sides, wholly immersed in the 

 ccenenchyma. 



Most, if not all, of the species when young form incrusting groups 

 or plates. In this stage new corallites are formed around the margins 

 from exothecal buds. Massive or unbranched species sometimes have 

 scattered axial corallites, scarcely more prominent than the others. 



The porous ccenenchyma is usually scanty in the smaller branches, 

 but often becomes abundant in the basal mass and larger branches. 



The septa are usually 12, in two cycles, those of the second cycle 

 being narrow and thin, and often rudimentary or entirely lacking. 

 The directive septa are usually wider than the others, and often 

 unequal. Sometimes all the septa are nearly abortive. 



In several species a few larger or giant calicles occur, with 24 septa. 



The surface of the ccenenchyma varies much in character and often 

 furnishes useful specific characters, but it is liable to vary on differ- 

 ent parts of a single specimen, according to age and other conditions. 

 It is commonly porous or pitted, and more or less thickly covered 

 with minute rough or sharp spinules or granules. 



The walls of the corallites ma}^ be regularly costulate, or else 

 covered with granules, either in rows or densely grouped. These 

 differences afford useful specific characters, but are liable to vary. 



Brook (Cat. Mad., 1893) recognized 220 species. Probably many 

 of these will be united when larger series can be compared. Prob- 

 ably Brook has attached too much importance to variations in modes 

 of growth. 



I have studied about 120 species, most of which seem valid, 

 including those described by Dana, a number of the types of Edw. 

 and Haime, and many others from China, the East Indies, Ceylon, 

 Red Sea, etc. But of many of these I have not seen good series. 



The types of most of Dana's species collected by the U. S. Expl. 

 Exped. are in the U. S. National Museum. The first series of the 

 duplicates of that collection was early given to Professor Dana for 



Trans. Conn. Acad., Vol. XI. 14 January, 1903. 



