6 GUSTAF LINDSTRÖM. 



Upper Silurian strata of Malmö, a small island near Christiania. — - Length 135 milliin. 

 width at the calice of the same specimen 34 millims. 



On the annexed plate (fig. 14) I have figured the section of a fossil which I leave 

 without a clenomination as it is still only known in a few fragments, but nevertheless 

 shares in some of the characteristics of the Perforate corals. The fragments were found 

 at Djupvik, Eksta. The exteriör shape is cylindrical, curved and almost smooth, not show- 

 ing the least trace of costee nor of lines of 'growth. It has a wall of large thickness, solid 

 and compact and without any indication of a peculiar structure. No septa are to 

 be seen. The central mäss is filled with a very lax tissue of trabeculse which, as seen 

 laterally, are arranged in a sort of irregular network, as that in the Perforate corals. 

 Diameter 5 millim 1 ). 



COENOSTROMA DISCOIDEUM. Lonsdale. 



Plate, figs. 6—13. 

 One of the most striking features in the uppermost calcareous beds of Gotland 

 are the bands of large spherical or elliptical balls, which bands attain a thickness of at 

 least five swedish feet. They are nowhere more prominent than on the eastern coast of 

 the island at Östergarn. There is a little cliff some 90 — 100 feet above the sea, nained 

 Grogarnsklint and from its northernmost point such a stratum of large balls, loosely ce- 

 mented together by a soft marl containing Brachiopoda and other fossils, can be followed 

 for half a swedish mile (three english miles) along the shore, gradually dipping towards 

 southeast, untill at its southernmost point it is at a level with the sea. There the balls 

 may be examined at leisure and are found to consist of an organic structure more 

 easily seen in prepared slices, if ground down and polished for the microscope. This 

 extensive bed is indeed a conglornerate of such large balls, of which some measure above 

 one english yard in length. This same stratum is spread far and wide över the island 

 and found, exactly in the same position as at Östergarn, in the hill of Thorsburg, so renowned 

 in the old legends of the natives and clistant more than a swedish mile from Östergarn. 

 The balls are moreover the chief components of those detached rockpillars 2 ) left be- 

 hind as remnants of denudated strata of the limestone. Wherever in the härd limestone, 

 which is entirely made up of fragments of crinoicls and corals, there are seen some of 



*) Sinee the above was printed Prof. Al. Winchell has kindly sent me specimens of Idiostroma caespitosum, 

 described by him from the Devonian strata of Michigan, and I find that my fossil is nearly related to it, 

 although differing from it and other Perforata in the immense thickness and thorough compactness of its 

 walls. 



2 ) Helmersen in »Geologische Bemerkungen auf einer Reise in Schweden» says p. 12 of these rock pillars: 

 »Die Hauptmasse biidet Stromatopora concentrica» and he gives a figure of balls measuring 4 feet in length. 

 Sir Roderick Murchison in »The Silurian Rocks of Sweden» (separately printed from Qu. Journ. Geol. 

 Soe. 1847) p. 20 ealls them »ballstones» and also figures some pillars. These pillars are by far more numerous 

 on the east coast of Gotland and are renowned sirice the' times of Linn^us (Gotländska Resa p. 218) 

 They have the native name of »Raukar», an old word probably derived from the icelandic »hraukr», siguify- 

 ing soraething elevated or what rises in the air, a roundish heap or knoll. 



