3o6 TABULATE CORALS. 



closed in the adult condition by a thin calcareous membrane. 

 In no case are septa present. 



From the Hcliolitidcg, Fishdipora is separated mainly by the 

 total absence of septa in the latter ; but, as has been pointed 

 out, there is a striking resemblance in general structure between 

 certain species of Fishdipora, on the one hand, and the species 

 oi Propo7'a and Heliolites on the other hand. " Mural pores" 

 have not been detected in any typical form of Fishdipora ; but, 

 as has been previously mentioned, Dr Rominger has shown 

 (Foss. Cor. of Mich., p. 29) that the coral described by Mr 

 Billings from the Devonian of Canada, under the name of 

 Fishdipora Catiadensis, is provided with perforate walls, and is 

 therefore a genuine Favositoid type. We thus have a coral 

 which precisely resembles the normal forms of Fishdipora in 

 appearance, but which exhibits mural pores ; and it becomes, 

 therefore, a matter for future research whether or not these 

 structures occur in any other species now referred to Fishdipora. 



The genus Fishilipora ranges from the Silurian to the Car- 

 boniferous, and I shall briefly describe the following three 

 species as illustrating its more characteristic features. 



Fistulipora minor, M'Coy. 



Fistulipora minor, M'Coy, Ann. Nat. Hist., ser. 2, vol. iii. p. 130, 1849; 

 and Brit. Pal. Foss., p. 79, 185 1. 



Spec. C/^r.— Corallum in the form of thin, irregular crusts, 

 attached parasitically at one point or over the whole lower sur- 

 face, attaining a thickness of two or three lines. Large corallites 

 oval or circular, about a fifth of a line in their long diameter ; 

 separated by interspaces of about their own width, less or 

 more ; and with few or no tabulae, these structures, when pres- 

 ent, being horizontal. Small tubes angular, of variable shape, 

 generally about a tenth of a line in diameter, each of the larger 

 tubes being surrounded by a single circle of the smaller coral- 

 lites, so that there exist two rows of the latter between any 



