ORDERACTINOIDEA. 61 



6. Rude hillocks, gibbous or nodular masses : many Porites, Alveo- 

 porfe, and some Astra?a3, Meandrinte, Gemmiporse, and Manoporse. 



7. Plates incrusting dead corals, in some species, sending up rude 

 branchings: many Manoporse, Milleporse, Agaricite. 



8. Simple and branched columns and club-shaped masses : many 

 Porites, Gonioporte. 



9. Clustered leaves or folia, which may be erect, as in some Mille- 

 porse, Pavonise, and Echinoporee; or, spreading from a base, and 

 rolled round one another, as in certain Gemmipora?, Manoporae, Echi- 

 noporfe ; or, clustered into convex or hemispherical clumps by up- 

 ward and horizontal growth from a centre, as in many Merulina?, 

 Pavonise, Tridacophyllise. 



10. Clumps of clustered branches from a common base ; a mode of 

 growth described as cespitose, and often producing very regular hemi- 

 spherical zoophytes, as in many Mussce, Euphylliaj, Caulastrsefe, Caryo- 

 phyllise, Porites, and Madreporfe. In many species of the last two 

 genera, the branches often grow together by coalescence. 



11. A horizontal network of branches spreading outward and bear- 

 ing erect branchlets : many Madrepores. 



12. A horizontal plate produced by a complete coalescence of hori- 

 zontal branches, and bearing above short finger-like branchlets : many 

 Madrepores. 



13. The spreading tree, a mode of growth styled arborescent: 

 many Madreporfe, Dendrophyllise, Gorgonidse, and Antipathes. 



14. The slender twig, either clustered or simple, straight or twisted : 

 many Gorgonidfe and Antipathes. 



15. Fan-shape, or with the branches spreading in a single plane, a 

 form styled flabellate : many Gorgonise. 



16. Reticulate; produced by a coalescence of branches and branch- 

 lets into a kind of network : some fan-shaped Gorgonise and the Aulo- 

 porfe; also, less perfectly in some horizontally-growing Madreporse. 



17. Pinnate, where the branchlets proceed regularly from opposite 

 sides of the branches : some Gorgonidfe and Antipathes. 



18. Clumps of clustered parallel tubes, united or not at intervals 

 by transverse plates or processes : Tubiporfe, Cornularise, Syringo- 

 porfe. 



19. Similar to the last, but the tubes embedded below in a loose 

 calcareous mass : Anthophylla. 



These varieties of form are illustrated in the accompanying Atlas. 



16 



