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The Genus ANACROPORA, Ridley. 



I. HISTORICAL. 



This genus was founded by Mr. S. 0. Eidley in 1884* to contain a small branching 

 stock, from Keeling Island, wliich was neither a Madrepore nor a Montipore. From Madrepora 

 it differed not only in the absence of any axial coraUites, but also in the fact that the tips 

 of the branches were composed of undifferentiated coenenchyma. The young calicles 

 developed in this tip, so that each new calicle appeared above that last formed. This 

 method of growth Eidley called " centripetal," whiLe that of Madrepom was called 

 " centrifugal," because the daughters appeared below the central or apical polyp. 



The coral was also apparently not a branched Montipore (although nearer to that 

 genus than to Madrepora), because the calicles were slightly protuberant, a feature not 

 typical of the Montiporce; and, again, the undifferentiated coenenchymatous tips of the branches, 

 without calicles, was thought by Eidley not to occur in Montipora. To this supposed 

 peculiarity of the new specimen the generic name Anacropora referred. 



On account, then, of the supposed fundamental difference in the methods of budding 

 between Madrepora on the one hand, and Montipora and Anacropora on the other, Eidley 

 suggested the formation of the two sub-families, Madreporince with the genus Madrepora, 

 and the Montiporinfe with the genera Montipora and Anacropora. This is the arrangement 

 here adopted, although on an entirely different line of argument. 



In the same year 1884, iu revising Milne-Edwards and Haime's system of the Madre- 

 poraria, Duncan f accepted the genus, definitely associating it with Montipora. The two 

 together formed the " Montiporoidea," which was the second alliance of the Poritidse, 

 Duncan in this returning to MUne-Edwards' association of Montipora with Poritcs rather 

 than with Madrepora. (See introduction to genus Montipora) 



In 1886, Quelch described two new species collected during the 'Challenger' expedition, 

 one from Banda and the other from Kandavu. He placed the genus near the end of the 

 Madreporidae after Astrceopora, and before Montipora, which genus, probably as some 

 concession to Duncan, was made to lead on to the next family, the Poritidte. 



In 1892, Dr. Eehberg, in his account of the Madreporaria in the Hamburg Museum, 

 described a new species {A. spinosa), from the Pelew Islands, differing remarkably from the 

 three species already described, not only in being covered with long thorn-like processes, 



* Ann. and Mag. Nat. Hist., xiii. p. 289. t Journ. Linn. Soc. Zool., xviii. p. 192. 



