ANTHOZOA 101 



phylogeny of Heliolites, and leads to the conclusion that that genus 

 and its allies constitute a specialised offshoot from the early 

 Zoantharia. The great interval of time between the last appearance 

 of Heliolites and first appearance of Heliopora lends some support to 

 the view that these genera are not closely allied ; the former and its 

 allies are not known in rocks of later age than the Devonian, while 

 the latter has been recorded in rocks of Cretaceous and later date 

 only. Poli/tremacis, found in the Cretaceous, is allied to Heliopora. 



Plasmopora. Allied to Heliolites. Usually discoidal or 

 hemispherical. Walls of smaller tubes incomplete or absent, and 

 their tabulae forming a vesicular tissue. Septa in corallites lamellar, 

 and prolonged outside each calyx, so as to enclose large spaces of 

 uniform size. Basal epitheca with concentric ridges. Ordovician 

 to Devonian. Ex. P. petaliformis, Silurian. 



Propora. Allied to Plasmopora. Edges of calyces projecting ; 

 septa represented by spines, and not prolonged outside the calyx 

 to enclose large spaces. Ordovician to Silurian. Ex. P. tubulata, 

 Wenlock Limestone. 



Halysites. Compound ; corallites long and tubular, arranged 

 in a single row and united at their sides so as to form lainina?, which 

 intersect ; in some species the corallites are of two sizes — the 

 smaller perhaps represent the ccenenchynial tubes of Heliolites- 

 Epitheca thick. Septa absent or represented by spines. Tabula? 

 well developed, horizontal or concave. Llandeilo Beds to Wenlock 

 Limestone. Ex H. catenularia, Wenlock Limestone. 



Chxtetes. Massive, often laminar, consisting of slender, 

 tube-like polygonal corallites ; walls without perforations. Tabula? 

 few, widely separated. Chiefly Carboniferous. Ex. C. radians. 

 The systematic position of Chcetetes is uncertain ; by some authors 

 it has been referred to the Polyzoa. 



Distribution of the Anthozoa 



From the point of view of their distribution at the 

 present day, the Madreporaria may be divided into two 

 groups, the solitary and the reef-building. 



