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



It is certain that several of the forms admitted as " species " hj 

 Brook in this group are very closely related, and perhaps are mere 

 local or growth-varieties of one species. The A. corymhosa (Lam.) 

 as restricted and described by Brook, from the type, with its several 

 varieties, belongs to this series, and bears the eai'liest name. 



It seems to me probable that a carefnl study of a good series of 

 specimens would compel us to unite A. surculosa, A. turhinata, A. 

 armatu, and A. symmetrica as varieties of A. corytnbosa. It may 

 also become necessary to unite with these A. cytherea and A. cythe- 

 rella, as somewhat more marked varieties. 



All these foi'ms are essentially alike in form and mode of growth ; 

 in the structure of the corallites; and especially in the rudimentary 

 condition of the septa. All have an abundance of rather large, 

 open, immersed calicles on the larger branches. 



Brook puts all these forms in section C of his subgenus Poly- 

 stachys, but he puts snrculosa in subsection c, and the, rest in sub- 

 section a. 1 can see no grounds whatever for this distinction; more- 

 over these forms do not, as a rule, conform with the characters 

 given by him for his section C. 



Some of the forms refeiTed to corymbosa by Klunzinger (as his 

 fig. 1, pi. iv, and fig. 2, pi. 1) seem to me very difPerent from the 

 corymhosa of Brook (after Lam.), although admitted by Brook, with- 

 out question, in his synonymy. 



As photographed by Klz., the radial corallites are speading and 

 have a decidedly thickened outer lip, while Brook states the outer 

 lip is " half -tubular or labellate " and " very fragile." Moreover the 

 Red Sea form is represented as having much larger and stouter 

 branches than the type. 



This stout-branched Red Sea form, with thickened walls and stout 

 lip to the corallites, seems to me a distinct species. I have examined 

 several specimens of this sort, from the Red Sea, but have not seen 

 a good series. 



For the same reason, I have not thought it desirable, at this time, 

 to formally unite all the forms, mentioned above, as varieties under 

 A. corymbosa, for of some of them I have seen only single examples. 

 Far better series are doubtless to be seen in the British Museum and 

 probably, also, in the large collections of South Pacific corals recently 

 added to the Mus. Comp. Zoology by Mr. A. Agassiz, but which I 

 have not yet seen. 



The 31. corymhosa of Dana is a very different species. See A. 

 urceolifera, p. 251. 



