ORDER ACTINOIDEA. 61 



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

 porse, and some Astrsea?, Meandrinae, Gemmipora, and Manoporse. 



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

 branchings : many Manoporse, Milleporee, Agaricise. 



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

 Porites, Gonioporse. 



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

 porse, Pavonire, and Echinoporse; or, spreading from a base, and 

 rolled round one another, as in certain Gemmiporee, Manoporse, Echi- 

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

 ward and horizontal growth from a centre, as in many Merulinae, 

 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 Mussse, Euphyllias, Caulastrsea3, Caryo- 

 phyllise, Porites, and Madreporae. 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 Madreporse, Dendrophylliee, Gorgonidse, and Antipathes. 



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

 many Gorgonidse 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- 

 porse ; also, less perfectly in some horizontally-growing Madreporae. 



17. Pinnate, where the branchlets proceed regularly from opposite 

 sides of the branches : some Gorgonidse and Antipathes. 



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

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

 porse. 



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. 



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