1895.] Study of Madreporavian Types of Corals. 



13 



occur chiefly in Funginae and Eupsammidae, rarely in Lophoserinae, 

 and never in Astraeidae. The author regards true synapticulae as 

 basal structures representing modified dissepiments. The advantage 

 of synapticulae to the polyp is that they afford a basal support over 

 which the fleshy parts and mesenterial loculi may bend and be con- 

 tinued to some depth. The author, in pointing this out, refers to the 

 analogy of the internal canaliculate visceral system thus produced 

 with the external canaliculate system attained by a porous coenen- 

 chyme in " Perforate " colonies. At the same time she thoroughly 

 disagrees with the prevailing opinion that the synapticulate types 

 have any nearer relationship with Madrepora, Porites, &c, since the 

 skeletal parts show many important differences of structure ; neither 

 is the " porous ccenenchyme " in any way homologous with the syn- 

 apticulate calyx. 



No essential difference is presented between septa, costae, and wall 

 in respect of their microscopic structure, and the author found it also 

 for other reasons practical to distinguish in her work the septa and 

 costae under the inclusive name of radial structures, the wall, on the 

 other hand, as a tangential structure. Dissepiments, tabulae, true 

 synapticulae, and certain kinds of columella are regarded as basal 

 structures. 



The microscopic structure of dissepiments and tabular is demonstrated 

 by the author to be the same. Both are composed of a series of cal- 

 careous growth-lamellae laid down from one surface only of the aboral 

 body-wall of the polyp. The fibro-crystalline deposit is therefore 

 perpendicular to the plane of contact between polyp and skeleton. 

 The distance from one platform of dissepiments to the next above 

 coincides in all typical Astraeids with the interval between two 

 growth-lines on the septal surface. It may be deduced from this that 

 the polyp lays down a new basal support for itself at the close of 

 each growth-period. The solid calcareous deposit (usually called 

 " stereoplasm " or "endotheca") at the base of the short, simple 

 calyces of most Turbinolids, has the same microscopic structure as 

 tabuiae or dissepiments, differing from them only in the fact that the 

 new groups of growth-lamellae are always closely opposed to the fore- 

 going. 



The " columellar " or " pseudocollumellar " area of recent Madre- 

 poraria is explained by the author as the morphological equivalent of 

 the ''tabulate " area in most Palaeozoic Madreporaria. The styliform 

 or fasciculate " true " columella of Turbinolia and its allies proves 

 itself to be, structurally considered, a basal deposit, and is merely an 

 upwardly arched or entwined modification of the tabulae. The 

 f pseudocolumella " is, as already known, a mixed structure in 

 which septal teeth or outgrowths unite with irregularly distributed 

 basal deposit. It finds its antetype readily in the occasional warping 



