GENERA OF CH^ETETID^E AND MONTICULIPORID^E. 305 



questionably congeneric, and that both must be united under 

 the older name of Fistulipora, M'Coy. The intimate structure 

 of the genus is also so nearly allied to that of certain Monti- 

 culiporte, as well as to Constellaria, that I think it is best to 

 regard Fistulipora as only a sub-genus of Monticulipora. 



The species of Fistulipora agree in the possession of a 

 dimorphic coral'lum, composed of two sets of corallites of con- 

 spicuously different sizes, and bearing definite relations to one 

 another. The large corallites are markedly circular or oval, 

 in most forms, and are isolated in position, while their cavities 

 are intersected by few and remote horizontal tabulae, these 

 structures being occasionally partially absent. The smaller 

 corallites are distinctly angular in form, and surround the 

 larger tubes completely, there being sometimes one and some- 

 times two rows between any given pair of the latter. The smaller 

 corallites are furnished with numerous and close-set tabulae, and 

 may or may not be bounded by complete walls. In the former 

 case the tabulae are complete and horizontal, whereas in the 

 latter case they anastomose with one another, and give rise to 

 a tissue of convex lenticular vesicles, the variations observable 

 in this respect being precisely parallel with those which obtain 

 respectively in Heliolites and Propora. The walls of the cor- 

 allites of both sets are thin, and are not conspicuously thickened 

 towards their mouths. It should also be borne in mind that 

 the interstitial and closely-tabulate corallites are sometimes 

 equal in size to the round and remotely-tabulate corallites which 

 they surround ; so that in speaking of the former as the " small " 

 corallites, we only employ this term in a conventional sense, 

 as indicating their homology with the small tubes of the Mon- 

 ticuliporoids generally. The corallum in Fistulipora often 

 exhibits " maculae " or definite areas occupied by the smaller 

 corallites only. These maculae may be stellate in shape ; but 

 they are never elevated above the surface or surrounded by 

 radiating elevated ridges, as is the case in Constellaria. Lastly 

 while the large rounded tubes always open the surface by open 

 calices, the intermediate angular tubes often have their mouths 



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