8 . GUSTAF LINDSTRÖM. 



completely overpowered by their mighty foe. On the surface of some colonies of Coeno- 

 stroma small Serpulae had fixed their shells and the next stratum of sclerenchyma was of 

 so extreme a thinness as not at once completely to cover these tiny shells. It was only 

 by adding fresh layers that Coenostroma with its deadly embrace forced the parasites 

 to direct the mouth of their shell upwards causing them to modify the shape of their 

 integument at the same time its own surface was altered thereby. 



It is from thus fixing itself on living Cyathophylla, and growing alongside their 

 stems and around the then living corals, that the peculiar shape of the Coenostroma from 

 Kräklingbo is derived. They resemble as nearly as possible the hills of the termites, 

 being conical, tapering, and ending in several points. When these points are broken a 

 Cyathophyllum is invariably found enveloped in their middle. These conical Coenostro- 

 mas attain a height of two feet or more. The variety which forms the ballstones origina- 

 tes in such a way, that it at first attachés itself to fragments, most of the cylindrical Rik 

 gosa, and grows completely round them without forming diskshaped colonies. By then 

 adding new layers around the central ones such large masses at last arise, entirely com- 

 posed of concentrical layers, and, judging by their bulk, they seem to have been the most 

 thriving of all varieties. Coenostroma occurs, besides at the. localities already mentioned, 

 also on Klinteberg, Stora Carlsö, Hoburg and many other places. 



If we now try to make out the affinities of this important coral, which so largely 

 contributes to the formation of the solid rocks of Gotland, we meet with the greatest 

 affinit}' as to the structure of the sclerenchyma in that family of the Anthozoa Perforata 

 called Poritidae by Milne-Edwards. It is indeed very difficult to see any difference be- 

 tween the spongious mäss of the Poritida? and Coenostroma if not that the former do 

 not commonly show any strata or interruptions in growth, but consist of one uniform 

 body. Some hemispherical Porites nevertheless exhibit such strata of different growth. 

 There exists also exactly the same appearance of the starlike calices in the tribe of the 

 Montiporina?, especially in the genus Psammocora, as may at once be seen by glancing at 

 the figures given by Milne-Edwards and Haime (Histoire Nat. Corall. plate E 3, fig. 3 b, 

 Psammocora obtusangula). Besides having its coenenchyma more dotted with asperities, 

 Psammocora is provided with a sort of coluinella, like a small rounded knob. In conse- 

 quence of what seems to point at real affinities I propose that Coenostroma be ranged in 

 the vicinity of the genus Psammocora of the Perforate family Montiporina?. Then all Recent 

 subfamilies of the Anthozoa Perforata, with exception of the Madreporinas, have repre- 

 sentative genera in the Palaaozoic formations. Thus the Eupsammiche were preceded by 

 Calostylis, the Turbinarias by the genus Prisciturben, lately founded by Dr Kunth of 

 Berlin 1 ), the Poritinaä by Stylaraaa in the Lower Silurian formation, and the Montiporinai 

 by Coenostroma in the Silurian and Devonian, arid probably also in younger formations. A 

 great many fossils both Palasozoic and especially from younger formations possess such 

 irregular stellate figures on certain parts of their surface as seen in the Montiporina?. 

 They are to be found in the group of fossils commonly called Petrospongia? by the au- 

 thors. The genera amongst them that most resemble our Silurian fossil are Stellispongia 



l ) Beiträge zur Kenntniss fossiler Korallen, Zeitsehrift d. Deutschen Geol. Gesellschaft, 1870 p. 82. I cannot 

 see auy difference between the intimate structure of the Eecent genus Millepora L. (M. Edw. & H. Hist. 



