KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 32. N:0 I. 71 



The original form of the calicles is that delineated in fig. 16, being perfectly 

 circular, witli thin margin, without indentations as låter acquired, fig. 11. Thore are 

 twelve regular, equal, short septal lamina^ with sharp, thin interiör edge. At much 

 regular distances (pl. xi, figs. 14, 17) short, thin spines go out from them, all directcd 

 downwards in a most characteristic inanner, contrary to what obtains in all other Helio- 

 litidte. These spines (figs. 14, 15) are often incrusted with microscopic crystals of ferric 

 oxide hydrate or manganous oxide hydrate which have oceasioned some confusion in the 

 descriptions by a few authors as if they were of organic origin. Such accumulations of 

 crystals also occur in the coenenchymal tubes as seen in fig. 15. In some instanccs the 

 septal spines are inclosed within a sheath of clear crystalline quartz all the way dowii, 

 giving the spines in a transverse section a peculiar appearance. 



The tabula3 are much distantiated, thin, oblique or horizontal. In the coenench3inal 

 tubuli again (fig. 17) they are more frequent, even as many as four on the space betwcen 

 two of the calicular tabulie. The narrow tubuli of the coenenchyma by and by expand 

 or widen and are changed into real calicles, as Sardeson already has observed. ^ This is 

 the same sort of coenenchymal gemmation which also occurs in Hel. hirsutus. 



Several varicties of Chajtetes and Monticulipora have sometimes been corifounded 

 with typical specimens of this coral, but they can be well distinguished upon closer 

 examination. So the Heliolites dubius var. minima of Ferd. Roemer, as he named some 

 specimens of a Monticulipora, distributed to foreign museums, but not described. It is 

 to such that he alludes in the Lethaea geogn. i, p. 506, where he says that some specimens 

 of Hel. dubius have maculai quite as Monticulipora. But in reality such specimens are 

 MonticuliporaB as I have assured myself through study of an original. 



Proheliolites dubius is entirely restricted to the uppermost strata of the Lower 

 Silurian formation. It is widely distributed in the Baltic provinces of Russia and dispersed 

 in the diluvial beds of North Germany, where Sadewitz in Silesia is one of the most 

 renowned localities. In Estland it occurs at Lyckholm, Kurkiill, Worras, Pattuka near 

 Worms and other places. In Sweden it has been found at Boda, Osmundsberg, Skatungbyn, 

 Lissberget and Östbjörka, all in Dalecarlia in the stratum which the Swedish geologists 

 have natned »Leptasna Limestone», corresponding to the Lyckholm and Borkholm strata 

 of Estland. It has also been found loose in a morainic accumulation on Gotland at Ojle 

 myr, from where Dr G. Wiman has dissolved out from the blocks by means of acids a 

 large collection of fossils probably belonging to a passage bed between the Lower and 

 LTpper Silurian, older than the Arachnophyllum stratum on the coast near Wisby. The 

 strata, of which these blocks are fragments, have not as yet been found in sitii. The 

 specimen delineated on pl. xi, figs. 16 — 17 has been kindly communicated by Dr Wiman 

 from the Ojle myr. 



1 Tabulaten, p. 272. 



