20 E. G. Carruthera — A Revision of some Carhoniferom Corals. 



naturally attracted by the notice in Nature of the surveys of the vessel 

 "Edi" and the cable-ship " Stephan " during 1903 and 1905 in ttie 

 western and south-western parts of the Pacific Ocean. Drs. G. Shott 

 and P. Perlewitz, in a paper i-eceutly issued in the Archiv dcr deutschen 

 Seewarte, taking into consideration previous work by U.S. sliip 

 "Hero" and of the German vessel "Planet," consider that these 

 soundings throw a great deal of new light on the configuration of the 

 sea bottom in those regions. They state that the troughs forming the 

 deeps are usually about 10 miles wide, excepting the Guam deep, which 

 is as much as 20 across. The most interesting statement to me is that 

 in their opinion the troughs are the result of subsidence occurring 

 on an enormous scale along lines of fracture, and that it is probable 

 the disturbances which produced these structures are comparativeh/ recent. 



In p. 316, "Evolution of Earth Structure," I have said that the 

 'deeps' in " my view are produced by a sagging of the earth's crust 

 similar to that which originated the Mediterranean basin," and further, 

 " They may not be verj' old and necessarily more lasting than the deep 

 basins in continental land such as the Black Sea and Lake Baikal." 



It is pleasant to find that these later investigations by practical men 

 tend to confirm my views and lead independently to similar conclusions, 

 especially as the explanation involves the origin of other features 

 of the sea bottom and the vexed question of the permanence of the 

 larger features of the oceanic areas. 



The narrowness of the troughs, if the fi.gures are reliable, is striking, 

 and points to vertical subsidence rather than lateral pressure. The 

 subsidence in so narrow an area would doubtless be accompanied by 

 fracture, but whether it is so or not we may legitimately infer, as 

 I have done, that the originating cause is a local shrinkage of the 

 magma under and beyond the area of the trough and deep down in or 

 below the lithosphere. 



The attainment of a reliable knowledge of the configuration of the 

 ocean bed can only be of slow growth. Thanks largely to telegraph 

 cable requirements, we have been adding to the facts in a fairly 

 liberal manner of late years. Let us hope that the good work will 

 continue notwithstanding the wireless phase of electrical development. 



V. — A KEvrsioN OF some Carboniferous Corals.^ 



By E.G. Carruthers, of the Geological Survey. 



Introduction. 



MORE than sixty years have now elapsed since the publication of 

 the classical monograph of MM. Milne-Edwards and Jules 

 Haime, " Les Polypes Fossiles des Terrains Palaeozoiques." It can 

 only be expected that many of the original descriptions of species 

 in that work have for long been in need of amplification and revision. 

 This applies with added force to the corals of the Carboniferous 

 Limestone, in view of the impetus given to the palaeontological study 



1 Communicated by permission of tlie Director of the Geological Survey of Great 

 Britain. 



