1899.] AStEJSiD 0OE.ALS FEOit THE SOTTTi PACIFIC. 7ol 



Genus Oebicella. 



Orbicella, Dana, Zooph. p. 205 (1848). 



Heliastrcea, Milne-Edwards & Haime, Cor. ii. p. 457 (1857). 



Heliastrcea, Duncan, Eev. Madrep., Journ. Linn. Soc, Zool. x\dii. 

 p. 104 (1885). 



Plesiastrcea, Milne-Edwards & Haime, Compt. rend, de I'Aead. 

 des Sc. xxvii. p. 494 (1848), and Cor. ii. p. 489 (1857). 



Plesiastrcea, Duncan, Eev. Madrep., Journ. Linn. Soc, Zool. xviii. 

 p. 107 (1885). 



Leptastrcea, Milne-Edwards & Haime, Compt. rend, de I'Acad. 

 des Sc. xxvii. p. 494 (1848), and Cor. ii. p. 493 (1857). 



Leptastrcea, Duncan, Eev. Madrep., Journ. Linn. Soc, Zool. xviii. 

 p. 119 (1885). 



Orbicella and Leptastnea, Klunzinger, Die Korall. des E. Meeres, 

 iii. pp. 43-50 (1879). 



There are in my collection 20 specimens of this genus, in 

 addition to which I have examined a ver}' large number of colonies 

 in the British and Cambridge Museums. 



The genus Plesiastrcea was separated from Heliastrcea by Milne- 

 Edwards and Haime iu 1848, and stated to have well-developed 

 pali before all the cycles of septa except the last, while the pali in 

 Heliastrcea are absent or rudimentary. In Heliastrcea acropora the 

 pali are exceedingly M'ell-developed before all the cycles of septa 

 except the last ; while in Plesiastrcea versipora the pali, although 

 generally very distinct, are in some calices not recognizable. 



Again, these two genera are stated to have their whole septal 

 edges toothed, while Lepiastrcm has the upper edges of its septa 

 entire and the lower edges toothed. This also is rather a question 

 of degree, for in Leptastrcea solidior, while the upper edges are 

 generally almost entire, in some calices they are finely and in 

 others very markedly toothed. 



One of my specimens, too, of Orbicella (Heliastrcea) heli&pora 

 presents calices which, examined separately as to the above 

 characteristics, would be placed in all the three so-called genera. 

 Indeed, any large colony of almost any species of these genera has 

 calices intermediate between those of the other two genera. 



Further, all these three genera have the same method of budding 

 and plan of structure ; and indeed, from the study of the hard 

 parts alone, there is no valid reason to separate them. Eor the 

 genus I have, following Klunzinger, employed the term Orbicella, 

 as it has clearly the priority, being first used by Dana for a sub- 

 genus of Astrcea. 



The genus Orbicella would then be characterized as follows : — 

 Corallites forming massive and incrusting colonies, sometimes 

 growing out into lobes, but usually forming rounded masses, 

 covered below by a distinct epitheca. Calices generally completely 

 separate, with the edges more or less prominent, often elevated. 

 Corallites joined together by exotheca only, the costae never being 

 continuous between calices, except where a young polyp has 

 recently been budded off. Calices usually deep and closed in 



