CORALS AND CORALLIFOL'M TYPES. 41 



(iutirely destitute of iuterual structures, or coutiiiiiiug in the great majority ol" oases : (1) 

 well developed tabula-, with or without radiating septa ; or (2), vesicular tissue with or 

 without tabuhe and septa ; or (3) a distinitly hexamerous or tetranierous system ol" septa ; 

 or (4) iudicatious of bilateral symmetry. 



The class, as thus defined, may be subdivided provisionally, and especially for deter- 

 minative purposes, into eight leading sections, as in the following scheme : 



Corallite cell entirely empty, i.e., witnout any internal structures : 



v^ 1. Vacuata (Type form, Aiilopora.) 

 Septa absent or quite rudimentary ; tabuhe well developed : 



§ 2. Tabtti:ata (Type form, Farosi/ts.) 

 Corallites united by a tubular or cellular c(i>nenchyme. 



s^ 3. Cellulata (Type form, Fislulipora.) 

 Tabuhe and septa both present. 



§ 4. Tabulo-Stellata (Type forms, Amplex/is, Zuphrenlis.) 



TabuliB central only, surrounded by area of vesicular tissue. Septa well 

 developed : 



§ 5. Vesicut.o-Stet>t,ata (Type forms, CyalhnphyUum, Lonsdalia.) 



Tabula- entirely replaced by irregular vesicular tissue : 



k 6. Vesiculosa (Type form, Cipiipfii/t/um.) 



Cell provided with an operculum composed of a single valve or of sevt-ral valves : 



§ 7. 0PERCUr..4.TA (Type form, Calceola.) 

 Cup or cell containing septa only ; tabula> absent : 



§ 8. Inteqri-Stellata (Type form, Pelraia.) 



§ 1. Vacuata : — The representatives of this section, distinguished essentially by their 

 tubular cells being entirely destitute of internal structures, an- of very doubtful position. 

 Very probably, they should be referred to the Alcyonaria or placed near the Serlulariaus 

 under the Hydro-medusa- : but nothing delinite, it is obvious, i-an be determined on this 

 point, and as the forms in question are of not uncommon occurrence in pakeozoic strata, 

 it has been thought advisable to retain them here, at least provisionally. They form but 

 one family, that of the Anlojwridir, (-ontainiug the following gimera : 



Fam. Aiiloporida; : — Corallum composed of short, tubiiiar or funnel-shaped empty 

 cells, united in branching groups : 



Sec. IV.. 1892. (I. 



