KONGL. SV. VET. AKADEMIENS HANDLIKGAK. BAND 32. N:0 I. 47 



The last stage of this instance, the tube which grew ou the surface of a polypary (sect. iv) 

 bears clearly the signs of degeneration, the coenenchyma so promising in the previous 

 stage is neai*ly gone, the theca and the septa are, as it were, shrivelled up. This bud 

 thus never attained to the perfection which is seen in many other small colonies 

 which have grown up on the surface of larger polyparies. An instance of this on a small 

 scale is given by the little colonj' in figure 35, where a similar tubular polj^pierite with 

 irregular coenenchyraal tubuli has procreated a smaller calicle. 



3. Epithecal gemmation. Though of an excessive thinness the epitheca must possess 

 strong vital functions where a t its formation it is covered by a diminutive lining of 

 living organic matter spred out from a polyp. I think that in no other way, than as 

 originating directl}' out of the epitheca, can be interpreted such a section as that shown 

 in iigure 12. There it seems to have been a little coenenchymal basis from which the re- 

 gular calicinal tube arose. 



Geological and Geographical Distribution. 



This species already appears in the Lower Silurian Strata of Russia. A specimen, 

 belonging to the Museum of Reval, by Dr Ki^R signed as Hel. parvistella Roemer, has 

 been found in the Lyckholmer Schicht of the Island of Worms and it is a variety with 

 small calicles. The same Museum also contains a specimen with uncommonly small 

 calicles only 0,s mm. in diameter from Hohenholm, Isle of Dagö. From the Upper Sil. 

 of Norway in Malmö near Christiania the State Museum preserves .specimens. In the 

 Upper Silurian of the Asiatic Russia at the Lower Tunguska and Olenek it has been found 

 by Russian explorers. ^ Richthofen found it in China at Tsien-shui."- It was found in 

 North Russia at Petschora.^ I have specimens from the U. Silurian of Bohemia (etage e^) 

 at Kotzel, from Dudley in England, from North America, Niagara formation, and sent 

 from Prof. James Hall as Hel. megastoma, from Drummond Isl., Michigan. It also 

 passes up in the Devonian formation, in the Middle Devoniau of the Alpi carniche of Italy 

 and also according to Milne Edwards and Haime in France at Néhou. 



In Sweden it occurs only in the Upper Silurian and in the Island of Gotland it is 

 one of the most common corals. The »Riks Museum» of Sweden is in possession of spe- 

 cimens from the following localities. 



a. From the oldest stratum of Gotland, the Arachopophyllum stratum in detached 

 pieces, broken up from the beds, which lie below the following strata. 



hc. From the next shale beds, the shores nortli and south of Wisby to Halls huk 

 and to Gnisvärd, Westergarn, Djupvik in Eksta, Lerberget in Stora Carlsö, Hablingbo, 

 östergarn, Lau (lower beds), Djupdj^a in När, Dember in Fårö, Kyrkbacken Färö. 



In the stratum d at Bunge Fårösund, Länsa Fårö, Ryssnäs Fårö, Kya-kbacken Fårö, 

 Tjelders Boge, the shore of Boge, Kulshage kanal Hangvar, the hills at Kålensqvarn, Wisby 

 and almost everywhere north and south of the town in the peculiar variety mentioned 

 above on p. 43, at Lau, Enviken in Hamra and at the hill of Hoburg. 



^ Lindström, Sil. Korallen aus N. Russlaud und Sibirien p. 9. 



- Richthofen, China vol. 4, p. 54. 



^ Keyserlincj, Wissensch. Beobacht. p. 175. 



