GENERAL ZOOLOGY. 73 



in the oldest strata, with genera distinct from, yet closely resembling, those 

 of the present day ; but even at that period all the existing families were 

 represented. In general the oldest forms of corals appear as flatter, lower, 

 more solid stems, inhabiting the bare rocky coasts, in that period before a 

 strand was formed, where they multiplied to a vast extent ; but in conse- 

 quence of the disconnected form of the rocks to which they were affixed, 

 they formed, as we see, no such great mural reefs as in later times, when the 

 unbroken lines of coast descending sheer into the sea, with a rocky bottom, 

 afforded a more suitable foundation to build up their stony walls. Certain 

 members, however, of the oldest Silurian Calcareous rocks — as the lime- 

 stone of Dudley, Schonen, Reval, Eifel (at Bensberg in particular) — seem 

 to be chiefly formations of coral, which, if not constructed quite as solid 

 reefs, are yet principally composed of the fragments of polypidoms. It is 

 remarkable that the shells of the Polythalamia, so abundant in recent times, 

 are almost entirely wanting in the most ancient coralline limestones. The 

 most probable explanation is the absence of flat coasts at that remote date ; 

 since the Foraminifera occur only in such situations, and at the present day 

 inhabit in the greatest numbers the lagoons of the coral islands, or the 

 channel between the reefs and the land to which they form a barrier. 

 There do not seem at that early period to have been any shallows of this 

 sort." 



" The coral formation shows itself in uncommon plenitude in the calcareous 

 rocks which constitute the base of the Carboniferous system. The Moun- 

 tain limestone, as well as the Dudley limestone, is at least partially, a vast 

 coral bank, to the formation of which the calcareous shells of Foraminifera 

 have largely contributed." 



" Similar phenomena continue to occur in the calcareous formations of 

 later date, almost all the sedimentary rocks of this class presenting local 

 evidences of ancient coral formations, being composed chiefly of the stems 

 and not of mere debris of corals. We may cite, for instance, the remark- 

 able Dolomites of Lubenstein and Altenstein, Konitz and Posneck, at the 

 south-western extremity of the Thuringian forest, not far from Salzungen, 

 which are standing yet unmistakeable rocks of coral, the reefs that once 

 bordered the narrow island ridge of that district, like those of the south- 

 west coast of New Caledonia at the present day. This is another evidence 

 that the former temperature of those seas was much higher than that now 

 prevailing in the Temperate Zone; as the coral animalcules cannot live 

 below 20°-23° of heat by Keaumur's scale. None but warm seas have 



