178 CONTRIBUTIONS TO CANADIAN PALEONTOLOGY. 



sharply crested. Root like, cylindrical excrescences from the side walls 

 of the polyparia, by which they are attached to other bodies, are a 

 peculiarity of the different species of Omphyma, which, however, are not 

 exclusively so to them, but are also noticed in other forms of the cyatho" 

 phylloid family. As another distinctive character of Omphyma, the 

 development of four septal fovese is mentioned by Milne-Edwards, but 

 they are generally not all equally distinct, while very frequently only 

 one of them is obvious, the others being almost obsolete. The genus 

 Ptychophyllum, described by Milne-Edwards as being organized like 

 Chonophyllum, differing from it in the twisted converging ends of the 

 radial lamella, forming a central false columella, is likewise in close 

 structural relationship with Omphyma, and in the special case of Ptycho- 

 phyllum jStokesii, I found its affinity with Omphyma verrucosa so great 

 that I altered the name of the first from Ptychophyllum to Omphyma" 

 (Rominger). 



Type species. — 0. (Madrepora) turbinata, Fougt. 



Range. — Silurian. 



The genus Ptychophyllum was founded in 1850, by Milne- Edwards and 

 Haime, with P. Stokesi, from the Niagara of Drummond Island, Lake 

 Huron, as the type species (not P. patellatum, Schloth., sp. as stated by 

 Zittel, in his Traite de Paleontologie, vol. 1, p. 232, French translation). 



If, as Dr. Rominger asserts, P. Stokesi is really an Omphyma (and he 

 has described it as such) then Ptychophyllum must be regarded as 

 .synonymous with Omphyma. 



Dr. Rominger in describing 0. verrucosa and 0. Stokesi, from Drummond 

 Island, the typical locality of both species, remarks that " it is sometimes 

 difficult to draw a line of distinction between specimens of these two 

 species." 



The genus Streptelasma, Hail, 1847, is classed by Dr. Lindstrom in his 

 " Index* to the generic names of palaeozoic Corals" as a synonym of 

 Ptychophyllum, Milne-Edwards and Haime, 1850, although why, if they 

 are synonymous genera, Ptychophyllum created three years later than 

 Streptelasma, should be retained in preference to Hall's genus is not clear 

 to the writer. However, the Zaphrentoid genus Streptelasma has no 

 affinity whatever with the Cyathophylloid genus Ptychophyllum. 



Omphyma verrucosa, Ratinesque and Clifford. 



Omphyma verrucosa, Rafmesque and Clifford. 1820. Ann. des Sci. Phys. de Bruxelles, 



vol. 5., p. 125. 

 ? Coral, Stokes. 1824. Trans. Geol. Soc, second series, vol. I., pi. XXIX., fig. 1 (on 

 the right). 



* Bihang till k. sv. vet.-akad. handl., band 8, No. 9. 



