122 



into upright pillars or pali, arranged in one, two, or three rows, 

 termed coronets. A transverse section of a simple coraUum 

 exposes all these parts. A longitudinal division shows sometimes 

 the existence of imperfect transverse partitions or dissepiments, 

 which, growing from the sides of the septa, interrupt the 

 continuity of the loculi. 



The septa have their sides sometimes covered with styliform 

 processes, which in general meet and form numerous synapticulce, 

 or transverse props, extending across the loculi like the bars of 

 a grate. In other cases the dissepiments are replaced by the 

 development of successive horizontal floors or tabulce, which do 

 not grow from the septa, but extend without interruption across 

 the entire space bounded by the theca. The costce are vertical 

 lines on the outer surface of the Polypary, corresponding in 

 position to the septa vrithin. The epitheca is an external 

 continuous calcareous sheath of epithelic sclerenchyma which 

 invests the Polypary. The visceral chamber is the central 

 cavity in which the body of the Polyp is lodged; in some 

 species it remains completely pervious from one extremity of 

 the Polypary to the other, and the membranous appendages 

 containing the reproductive organs situated in the loculi extend 

 to its bases : in other species a number of synapticulae extend 

 from one septum to another, at various heights, fill up the 

 lower part of the locuH, or partition it off by transverse 

 laminae or dissepiments, which grow from the sides of the septa 

 in an irregular manner, and do not form complete divisions. In 

 some Corals, where the septal apparatus is in a rudimentary 

 condition, the bottom of the visceral chamber is successively 

 raised by the formation of new floors or tabulae, which extend 

 horizontally across the Polypary, and form a series of cells or 

 chambers below the cahces. 



Professor J. D. Dana,* in his great work on Zoophytes, has 

 divided this class into two orders — 1st, the Actinoidea, — 2nd, 

 the Hydeoidea, 



• James D. Dana, History and Classification of Zoophytes. Plates. United 

 States' Exploring Expedition. Philadelphia, 1846. 



