KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 32. N:0 I. 91 



English speciinen. The characteristic costal radii are on these well expressed, but in the 

 deviating specimen fig. 8 there are no vestiges of thera and only shallow grooves radiate 

 irregularly from the calicles. This specimen is also interesting because it shows the 

 bladders of the coenenchyraa, which else lie concealed beneath the surface and accessible 

 only in sections. These convex lamellte are completely covered by diminutive wartlets, 

 the bases of the acute, which are so numerous in the interiör on the convex lamellre. 



In the variety, fig. 11, there are not the faintest traces of the grooves and there 

 is a nearly even coenenchyma covered with blunt warts. This and similar specimens 

 constitute a variety by themselves, as the interiör structure also is deviating (tigs. 12, 13) 

 with thick calicular thecse, longer and larger septal spines, the aculaj also thicker than 

 else. These varieties have grown in ovate, sphferoidal or irregularly globular masses and 

 consequently no epitheca is seen. The calicles are deep and the rim is composed of twelve 

 noduli, exactly corresponding to the exteriör end of a septum, fig. 11. In fact, these noduli 

 are the bases of a new or the youngest series of septal spines which through the growth 

 of the corallum become placed more and more deep in the calicular cup, at the same time 

 extending in length and resembling the older ones. The tabulaj are thin, much distantiated, 

 horizontal, sometimes with aculse on their upper side. Such species as these are derived 

 from the strata cl of Gotland coöval with the Wenlock limestone of England. From far 

 deeper strata, those of Borkholm, F"^, we have specimens which may be considered as the 

 oidest of this species. They are diskshaped or slightly domeshaped, the calicles are more 

 widely apart than in the younger, the coenenchyma nearly as in the variety fig. 11. 

 (Figs. 18, 21, 22.) The septa are short, and broad, and reach only a little distance from 

 the calicular theca (fig. 18). The coenenchyma is composed by uncommonly small, convex 

 lamellaj and the aculaj are thick and broad (fig. 19). 



I have ventured to join with these forms some which have for a long time been 

 considered as belonging to the nearly related genus Lyellia. I have treated more in full 

 further down about this genus and there given my reasons why I consider that it cannot 

 be retained, as the species enclosed within it, partly cannot be distinguished from Propora, 

 and partly must form a new genus. The two species which I consider as belonging to 

 Propora and hardly to be separated from Pr. tubulata, are. Lyellia americana (pl. viii, 

 figs. 24 and 25), and Lyellia parvituba (figs. 29 — 31). It is to be borne in mind that the 

 specimens which I have seen, especially the former from Point Detour, Michigan, have 

 been much altei^ed through being silicified. Still they retain the characteristic features 

 of their organization. In Lyellia americana the septa are larger, but resemble those in the 

 English specimen of Pr. tubulata (fig. 5). In Lyellia parvituba (fig. 30) the septa again 

 are shorter, but resemble those in figs. 15 and 16. The coenenchyma of both coincides 

 as nearly as possible with that in fig. 10. The aculse are in Lyellia americana (fig. 25) 

 much enlarged through låter additions and in Lyellia parvituba (fig. 31) they are still so in 

 a much higher degree and the calicular tubes are partially filled by an exuberant crystalline 

 growth of later date. There is a third species, Lyellia glabra Edw. & H., of which I have 

 not seen specimens but which, to judge by the figures^, perhaps also belongs to Propora. 



^ Pol. terr. paljeozoiques, pl. 12, figs. 2 — 2c. Heliolites macrostylus QUENSTEDT, Petref.-Kunde, tab. 149, 

 f. 5, 6 is evidently identic with this species. He has also given a good figure (tab. 149, f. 9) of L. parvituba. 



