76 ORBICELLA 



ASTRiEACEiE M.-Edw. & H. 

 OEBICELLA Dana. 



Heliastrcea M.-Edw. & H. Hist. Nat. des Corall. 



Astrcea M.-Edw. & H. Compt. rend, de I'Acad. des Sc. 1848, and Ann. des Sc. Nat., 3' Ser., t. XI. 



The name adopted by Dana covers so nearly the same gronnd as 

 the generic division called Heliastraea by Milne-Edwards and Haime, 

 that it is retained here, as had already been done by Mr. A^errill in the 

 Bull. Mus. Comp. Zool., No. 3. 



Orbicella cavernosa Verrill. 



Madrepora radiata ? Ellis. {Astrcea, Heliastrcea, Orbicella radiala Anct.) 



Madrepora cavernosa Esper, Pflanz. Suppl., p 18, PI. 37.* 



Astrea argus Lamk. 



Tuhastrea cavernosa Blainv, 



Orbicella argus Dana. 



Astrea cavernosa M.-Edav. & H. Ann. des Sc. Nat., 3" Ser., t. XI. 



Heliastrcea cavernosa M.-Edw. & H. Hist. Nat. des Corall. 



Heliastrcea conferta ? M.-Edw. & H. 



There is considerable variation among the specimens from Florida in 

 the Mus. Comp. Zool., enough apparently to Avarrant placing them 

 among the three species named in the synonymy; but by carefully 

 examining the different parts of each specimen, passages from one to 

 the other can be found. Thus young polypidoms, expanding rapidly 

 laterally, and with rather distant poljqDS, appear at first to difter con- 

 siderably from strongly convex ones with crowded calicles ; the costre 

 are longer, flatter, and less sharply denticulate, and the border of the 

 calicles less elevated. 



The size of the calicles, relied on to divide the genus into groups, by 

 Milne-Edwards and Haiine, is a very uncertain character ; one specimen 

 has in one part the calicles varying from 3.5 to 4.5 mm., in another part 

 from 7 to 8 mm. The same specimen has in some parts the contiguous 

 walls united solidly, with very few or no exothecal cells, in others sep- 

 arated by an abundant cellular exotheca. In worn specimens the last 

 cycle disappears first, for that reason proljably OrbiccUa {Madrepora) 

 radiata Ellis has been characterized b}^ Milne-Edwards and Ilainie as 

 having but three cycles. 



This coral is generally found from 2 to 15 flithoms deep, forming 

 sometimes masses of considerable size. It is also occasionally found in 

 smaller masses in lesser depths on the reef 



* I have not seen this figure, the (.up^ of Espir wliicli I have consulted being ineonipUte. 



