102 COELENTERATA—ANTHOZOA SUB-BRANCH II 
Corallum commencing with prostrate basal network similar to Aulopera. 
Numerous species ranging from Silurian to Carboniferous. 
Chonostegites, E. and H.  Corallum massive; cylindrical corallites con- 
nected by horizontal, hollow, laminar expansions into which the endothecal 
tissues are directly continued; tabulae oblique, cystoid. 
Devonian. 
Thecostegites, K. and H. Corallum encrusting ; corallites 
short, cylindrical, and connected by thick horizontal plates. 
Tabulae approximately horizontal ; septa twelve in number, 
represented by marginal ridges. Devonian. 
Family 4. Halysitidae. Milne-Edwards and Haime. 
Chain corals. 
Corallum composed of long, cylindrical, laterally compressed 
corallites, which are joined to one another only along the more 
constricted edges, and form free, vertical, intersecting, and an- 
Hee be: astomosing laminae. Wall thick, covered on free sides by wrinkled 
Halysites catenularia As 4 oo 8 or 
Lin. sp. Silurian: Gott. @pitheca , tabulae numerous, horizontal, or concave ; septa repre- 
eee SEMI Te sented by vertical ridges or rows of spines, in cycles of twelve, 
sometimes entirely absent. Increase by stolonal gemmation. 
The single genus Hulysites, Fischer (Catenipora, Lam.), (Fig. 182), comprises 
two groups of species ; those in which the corallum is composed throughout of 
corallites of equal size (1. escharoides, Lam. sp.), and others in which any two 
of the larger corallites are separated by the intervention of a single smaller, 
closely tabulate tube (H. catenularia, Lin.) Ordovician and Silurian ; maximum 
in Silurian. 

Family 5. Chaetetidae. Milne-Edwards and Haime. 
Massive coralla, composed of fine, subequal, tubiform corallites, contiguous on all 
sides. Calices rather irregular in shape, one diameter slightly greater than the other. 
Walls thoroughly amalgamated, common to adjacent corallites, imperforate, apparently 
composed of closely arranged, ankylosed vertical columns, which terminate at the surface 
in hollow prominences. Septa absent, but one or two tooth-like projections often observ- 
able in sections. Tabulae horizontal, remote or abundant. 
All the forms belonging to this family are extinct, and occur chiefly in the 
Ordovician, Silurian, Devonian, and Carboniferous systems; but they are also 
found sporadically in the Trias, Jurassic, and Cretaceous. They are important 
as being largely concerned in the formation of Palaeozoic coral reefs, especially 
during the Ordovician. Milne-Edwards and Haime regarded them as An- 
thozoaus, Rominger and Lindstrém as Bryozoans ; while Dybowski, though 
admitting their resemblance to certain Bryozoans, emphasised their affinities 
with the Favositidae. By Nicholson they were assigned to the Octocoralla, for 
the reason that the corallites frequently exhibit a dimorphous character the 
same as in Leliolites and Heliopora, besides agreeing in their microscopic 
structure with /Heliolites ; while in addition they possess well-developed tabulae 
and imperforate walls, and increase by intermural gemmation or by fission, 
Nevertheless, their resemblance to certain of the cyclostomatous Bryozoans 
(Heteropora) is fully recognised by Nicholson, and insisted on by Ulrich. 
Chaetetes, Fischer (Figs. 183, 184). Corallites long, thin- walled, prismatic, 
