THECID^E AND HELIOPORIDJE. 249 



to the fact that the section has happened here to traverse 

 a line lying between several of the larger corallites.) 



Accepting the above views as to the true structure of the 

 corallum of Propora, it seems clear that the genus agrees in 

 substantial characters with Plasmopora, with which therefore 

 it should be united. The species which have been referred 

 here are Upper Silurian in their range. (The supposed Car- 

 boniferous species is a Palaacis.) 



Genus LYELLIA, Edwards and Haime, 1851. 



(Pol. Foss. des Terr. Pal., p. 226.) 



(PL XL, figs. 4, 4 a.) 



Gen. Char. " Corallum massive ; corallites cylindrical, with 

 thick and costulated walls, free towards their terminations, and 

 united throughout the remainder of their length by a very 

 abundant vesicular ccenenchyma ; visceral chambers traversed 

 by somewhat irregular tabulae ; septa twelve in number, well 

 developed " (Edwards and Haime, loc. cit.) 



Obs. The genus Lyellia was founded by Edwards and 

 Haime to include two species of corals (L. Americana and 

 L. glabra) from the Upper Silurian of North America. Other 

 species of the genus have been described by Dr Rominger 

 (Foss. Cor. of Michigan, p. 14), from deposits of the same 

 age ; and it is probable that some of the forms of Heliolites 

 (e.g., H. affinis and H. speciosus] described by Mr Billings 

 from the Lower and Upper Silurian deposits of Anticosti, 

 are really referable to Lyellia (Cat. Sil. Foss. of Anticosti, 

 pp. 5 and 30). I have not myself been so fortunate as to 

 meet with any examples of this genus, and am therefore 

 able to say nothing as to its minute internal structure. 

 Judging from the descriptions and figures of the above- 

 mentioned authors, Lyellia would seem to be nearly allied 

 to Plasmopora, and especially to those forms of the genus 

 which have been usually separated under the name of Pro- 



