308 



ZOANTHARIA. 



corallum (fig. 189) is cylindrical, and may be simple, or may become 

 composite by the production of lateral buds. The wall is thick and por- 

 ous, but is covered here and there with a thin striated epitheca. The 

 septa are so highly perforated as to become more or less trabecular (fig. 

 189, B and c), and they may unite centrally to form a species of spongy 

 columella ; but dissepiments are very imperfectly developed. There is 

 no reason to doubt the correctness of Lindstrom's reference of Calostylis 

 to the Eitpsammidce, with which the genus agrees in all essential char- 

 acters. No type of the Eupsammidce has hitherto been detected in 

 any Palaeozoic deposit of later age than the Silurian, nor in any of the 

 older Mesozoic rock-groups ; but in the Cretaceous rocks we meet with 

 the genus StephanofiJiyllia. In this genus the corallum is free, simple, 

 and discoid, with an open circular calice ; and species of the genus 

 range from the Cretaceous to the present day. In Balanophyllia, 

 ranging from the Eocene Tertiary to the present day, the corallum is 

 also simple, but is usually permanently fixed to some foreign body. An 

 allied type is the Pliocene and Recent genus Thecopsammia, which is 

 considered by Professor Martin Duncan to be related in some respects 

 to the Silurian genus Calostylis. Also allied to Balci7iophyllia is the 

 Eocene genus Endopachys (fig. 190), in which the corallum is simple and 



Fig. 190. — Endopachys Maclnrii, viewed in profile and from above. Eocene Tertiary. 



compressed, and a spongy columella is present, while the keeled base is 

 continued into two wing-like expansions. The type of another group of 

 the EupsammidcE is the well-known genus Dendrophyllia (fig. 187), in 

 which the corallum is composite and generally of a dendroid form, the 

 corallites being cylindrical, and having a spongy columella. The species 

 of De?idrophyllia range from the Eocene Tertiary to the present day. 



Family 2. Madreporidce. — In this family the corallum is invariably 

 composite, the mode of increase being by gemmation, and the constitu- 

 ent corallites of the colony being united by an abundant spongy coen- 

 enchyma. The corallites have porous walls, which are not distinct 

 from the ccenenchyma, and the septa are usually fairly developed, 

 and are lamellar. The interseptal loculi have dissepiments, but a 

 columella is wanting. As here defined, the family of the Madepor- 

 idce includes only the single genus Madrepora, including a vast 

 number of forms, ranging in time from the Eocene Tertiary to the 

 present day. The corallum (fig. 191) in this genus is very variable 

 in shape, being most usually branched or tufted ; the corallites are 

 tubular, with more or less projecting calices ; and the visceral cham- 



