152 Terminology 



Mesenteries. The radial vertical lamellae of the soft polyp, com- 

 posed of mesoglea and endoderm. Upon their sides the 

 muscles are attached. 



Minor septa. The cycle of shorter septa which never extend 

 far into the calyx. They appear late in the development of 

 the corallum. 



Mural pores. Regularly spaced pores in the thin-walled Tabu- 

 lata. They are typically developed in the Favositidae. 



Pali. Rods or knobs formed by the lobation of the inner ends 

 of septa. 



Parietal columella. A columella which results from a speciali- 

 zation of some of the radial calicular structures such as 

 septa or pali. 



Peritheca. A calcareous deposit covering the base and sides of 

 a compound corallum. It is homologous with the epitheca 

 of a single corallum. 



Pores. See Mural pores and .Ipical pores. 



Primary septa. The first group of septa to appear — usually two 

 or four in Tetracoralla ; six or twelve in Hexacoralla. See 

 Major septa and Minor septa. 



ProtocoraUite. The corallite secreted by the protopolyp. 



Protopolyp. The parent of a colony of polyps forming a com- 

 pound corallum. 



Pseudotheca. A wall formed by the thickening and coalescing 

 of the outer portions of septa. See Eutheca. 



Quadriseptal arrangement. A pinnate grouping of septa, alter- 

 nately long and short. Typically, as in the adult form of 

 Cyathaxonia cornu, there are four in a bundle, but often 

 there are only three or two. 



Ruga; (pseiidocostce). Ridges on the epitheca. They alternate 

 in position with the costse and septa. 



Septa. Vertical radial partitions of the calyx secreted in fold? 

 of the basal disk. See Major, Minor, Primary, and Second- 

 ary septa. 



TohellcF. Small arched plates forming a part of the columella 

 in certain genera like Lonsdaleia. They slope upward and 

 inward toward the central axis. 



TahulcE. Horizontal plates extending across the whole cavity of 

 a single corallum or corallite. 



Theca. The outer wall of a corallite or single corallum, exclu- 

 sive of the separate outer layer, the epitheca, q. v. It may 

 be formed in various ways. See Eutheca and Pseudotheca. 



