38 THE VOYAGE OF H.M.S. CHALLENGER. 
Madreporaria, while he cautiously states that ‘‘ probably most of its genera are not 
Madreporarian.” ' 
In the following classification the Madreporaria are primarily divided into three 
sections. 
Section I. Madreporaria Aporosa (=Madreporaria Aporosa and 
Madreporaria Rugosa, Auctt). 
" II. Madreporaria Fungida. 
» ILI. Madreporaria Perforata. 
Section . MADREPORARIA APOROSA. 
The definition of this section, as hmited by Professor Duncan,’ needs but one slight 
alteration in the characters of the septa to make it applicable to the section, as 
extended above, to include the old Madreporaria Rugosa. The septa may be distinctly 
lamellate, and solid or cribriform, or indistinctly lamellate, becoming more or less 
vesicular. 
Professor Duncan also observes that ‘the hexameral arrangement of the septa is not 
constant ; it may be pentameral, heptameral, octameral, or decameral.”* To this should 
have been added that it may also be tetrameral.* 
The group Madreporaria Aporosa, as now extended, is defined as follows :— 
Madreporaria with simple or colonial forms. Hard structures usually solid and 
imperforate. Theca or wall solid, may be epithecate. Arrangement of the septa variable. 
Septa distinctly lamellate, and solid or cribriform, or indistinctly lamellate, becoming 
more or less vesiculate. Interseptal loculi open throughout, or closed more or less by 
endotheca in the form of dissepiments, tabule, and stereoplasm. Calicles of different 
shapes. 
This section is divided into three subsections, each of which is again divided into 
families. 
Subsection L. Turbinolida. 
i If. Oculinida. 
e III. Astraeida. 
Subsection I. TURBINOLIDA. 
This subsection is not treated of in the present Report, but is characterised as follows : 
—Corallum simple or in colonies without exotheca. Septal loculi open to the base. 
1 Journ. Linn. Soe. (Zool.), vol. xviii. p. 6. * Revision, p. 7. 
3 Revision, p. 7. 4 Vide Holocystis, Revision, p. 130. 
