MADREPORAKIA. 



The Family PORITID-ffi. 



HISTORICAL. 



The family Poritidae was founded by Dana in 1848* to contain two genera, Porites and 

 Goniopora. These were placed in the tribe Madreporacea, characterised by having polyps with 

 12-24 tentacles in a single ring, and with lateral gemmation. The Madreporacea were 

 divided into three families, — Madreporidse.f Favositidae.J and Poritidae. 



In this juxtaposition of the Poritidae with the Madreporidae Dana was following the lead 

 of Ehrenberg, on whose classification he greatly improved by recognising the structural 

 differences between the two. In the latter the calicles are deep and can be traced through 

 the corallum, while the polyps rise but a little way above their skeletal cups. In the 

 Poritidae the calicles are shallow, the skeleton fills up with reticulum, so that the calicles are 

 hardly traceable through the corallum, and the polyps rise high above the surface. 



The great divisions of Stony Corals, the Madreporaria aporosa and M. perforata, established 

 by Milne-Edwards and Haime, marked a great advance ; for the separation of the Eupsammiidse, 

 Madreporidae, and Poritidae from the rest of the Stony Corals has been fully justified. These 

 distinguished authors were not, however, guided by the knowledge we now possess as to the 

 morphology of the skeleton ; this is apparent the moment we come to their detailed treatment 

 of the families. Though at once § accepting the family Poritidae of Dana and improving on 

 Dana's arrangement so far as to remove the Favositidae (with the exception of Aheopora) 

 from any association with it, or with the Madreporidae, their removal of Montipora from the 

 Madreporidae, and their placing it among the Poritidae was a backward step. To this they 

 were led by their well-known theory of the origin of the coral skeleton out of calcareous 

 nodules. These they thought were joined end to end into trabecular lattice-works, the radial 

 portions of which in the higher forms became lamellate septa. According to this theory, 

 therefore, all corals in which the skeleton was wholly reticular, showed primitive conditions, 

 and were classed as Poritidae. Hence, in the description given of this family, we read, " Appareil 

 septal jamais completement lamellaire, et forme seulement par des series de trabecules qui 

 constituent par leur reunion une sorte de treillage " 



This theory, however, is unsupported by facts. The most perfect trabecular septa, accord- 



* The United States Exploring Expedition : Zoophytes, p. 549. 



f See Vols. I., II., III. of this Catalogue. The family Madreporidae is discussed in the Intro- 

 duction to Vols. II. and III. 



X This family " Favositidae " was quite artificial, and further the genera Favosites and Aheopora 

 have no connection whatever with Porites. 



§ C.K., xxix. (1849) p. 258, and Ann. Sci. Nat. (3°) xvi. (1851) p. 21. 



