100 G. LINDSTRÖM, HELIOLITIDiE. 



consider this purely inorganic phenomenon of corrosion as structural or organic and analogous 

 with the exteriör tabuloe of Tubipora. According to the authors of the »Polypiers paléozoiques» 

 this genus embraeed only two species: Lyellia americana and glabra. Of these I have 

 had occasion to examina the former and I have above page 92 given the results of this 

 examination. As there stated it shows a remarkable coincidence with sections of Prop. 

 tubulata (which see), so nearly concordant, that I do not hesitate to refer them both to 

 the same genus and even species. There may of course be some slight deviations in the 

 septal spines, else these, the coenenchymal lamellee, sparingly covered with aculae, the 

 remote tabulas in the calicular tube are nearly the same. 



The next species, L. glabi^a, I know only through the excellent iigures and descrip- 

 tion of MiLNE Edwards and Haime^ and they suffice for deciding that this also in all 

 particularities corresponds with a real Propora and that it, in case it is an independant 

 species, should be named Pr. glabra. 



Since Milne Edwards and Haime had published their grand works Rominger has 

 described^ three new species, L. papillata, decipiens and parvituba. Of these I have not 

 seen L. decipiens, but the exact description leaves no doubt that it is a coral of the same 

 type as Pr.? ambigua which has been described above and which perhaps constitutes a 

 new generic or subgeneric type. 



Rominger himself has sent me specimens of his L. parvituba. On pl. viii, figs. 29 — 31 

 I have represented this species. The corallum is disciform, covered by the densely placed 

 small osculating calicles, scarcely one mra. in width. Seen from above the septa are short, 

 thick, some radii extend outside the theca though not in immediate continuation with the 

 septa. Though consisting entirely of liniestone, it is interioi'ly so much altered, as almost to 

 defy any attempt to find out the original structure. Instead of being provided with ordinary 

 septal spines the calicinal tubes are at iri^egular intervals filled with large numbers of micro- 

 scopic crystalline glomerations heaped in masses above each other on the tabulaä and on the 

 interiör sides adjoining, and in a transverse section they are seen to cover the whole area of 

 the tabula. The coenenchyma is uncommonly irregular; extraordinary large lamellte in- 

 termingled with smaller. The calicular tubes are also of a highly irregular growth, inter- 

 rupted by coenenchyma as if overgrown by it and then beginning anew. But after all, de- 

 tracting from the abnormities, this species is so similar in its fundamental constitution to L. 

 americana and glabra that it must be placed in the genus Propora. If now, as I think, these 

 three species which did properly constitute the genus Lyellia have all characters in common 

 with Propora, as well as the allied Lyellia decipiens, and because the onlj^ remaining species, 

 L. papillata, as I will show further down, is widely different from the former it follows l:o) that 

 the genus Lyellia must be abolished^ and 2:o) that L. papillata constitutes a new generic type. 



Da VIS in his »Kentucky Fossil Corals» has given photographic figures of two other 

 Lyellia, viz. L. discoidea and L. puella. The descriptive letterpress of his work seems 

 never to have been published and the figures are too indistinct to give any help in identifjång. 



1 Pol. terr. pal., p. 226, pl. 12, iig. 2. 



^ Geol. Survey of Michigan, vol. ili, pl. ii. Palseontology, p. 16 — 17. 



^ The genus Protolyellia proposed by Torell does not show the least affinity with Lyellia or Propora 

 and is in fact no coral at all. See for further particulars ;?Fragmenta Silurica», p. 31. 



