MADEEPOEA. 23 



3. Axial corallites slender, elongate, cylindrical ; margin plane or suddenly 

 contracted, not rounded. Wall thin but dense. A second cycle of septa 

 is not present Tbachtlopoba, p. 184. 



Division IV. — Axial corallites more or less distinctly compressed, giving rise to flattened branches, 

 with the most prominent corallites confined to the lateral margins. 



DlSHCHOCTATHUS, p. 192. 



Division I. 



1. Subgenus EUMADREPORA. 



This section of the genus includes the majority of the arborescent species, together with 

 others in which the original ramose condition is lost by fusion of adjacent branches. The 

 species of the cyclopea group form massive lobes or plates ; but the characters of the axial 

 and radial corallites show an affinity to M. muricata f. palmata. Unless the branches 

 are confluent quite to the apex the axial corallites are 2"5 mm. exsert or more. The radial 

 corallites are rarely immersed on the distal divisions of independent branches, and the form 

 varies from nariform either through tubo-nariform to tubular, or through half-tubular to 

 labellate and dimidiate. The axial corallites possess a star of 12 septa, of which the pri- 

 maries are subequal. In the radial corallites there are also usually 12 septa, unless in young 

 corallites; but the directive septa are generally more prominent than any of the others. 

 Corallum usually reticulate in section. A number of slender arborescent species have been 

 provisionally included in the first section of the subgenus which show an affinity with the 

 tubigera group referred to Polystachys. The subgenus is also related through M. crassa to 

 the nobilis group of Tylopora, and to Lepidocyathus and Odontocyathus through the pocillifera 

 group. 



A. Prominent corallites subequal, nariform or tubo-nariform, more rarely some are labellate. 

 The radial corallites rarely bear buds unless in situations which indicate new out- 

 growths. 



a. Corallum arborescent ; branches terete, rarely coalescent, but in one variety o/M. muricata 

 become fused together into plate-like or vasiform specimens. 



* Branches over 1 cm. diameter. 



1. Madrepora muricata. 



Millepora muricata (part.), Linnaeus, Syst. Nat. ed. x. p. 792. 



Madrepora muricata (part.), Linnaeus, Syst. Nat. ed. xii. p. 1279 ; Pallas, Elenchus Zooph. p. 327 ; 



Ellis & Solander, Zoophytes, p. 171 ; Esper, Pflanzenth. Fortsetz. Th. i. pp. 45-59, pis. 1., li., 



liii. ?, liv. B ?, Ixxxiii. 

 1 Madrepora plantaginea, Duchassaing (nan Lamarck), Anim. radiaires d. Antilles, p. 17. 



A. Forma palmata. 

 Madrepora muricata, var., Esper, loc. cit. pis. li., Ixxxiii., liv. b ? 

 Madrepora infundibuUformis, Esper {non Linn.), loc. cit. pi. li. 



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