206 Mr. J. W. Kirkby on some additional Species 



Though palaeontologists have long been aware of strong re- 

 semblances existing between Carboniferous and Permian fossils, 

 it is only of late years that the extent and value of such resem- 

 blances have been made the subject of careful inquiry. Among 

 those who have wrought at this subject, there is perhaps no one 

 who has produced greater results than Mr. Thomas Davidson. 

 Most of the Brachiopods of the preceding list have been shown 

 to be both Carboniferous and Permian by his investigation. 

 And this authority is of the greatest value on the subject, and 

 will be held conclusive by most palaeontologists. I have, how- 

 ever, been able to examine and compare specimens of most of 

 the species myself, and thus in some degree to corroborate the 

 conclusions of this distinguished investigator. For an account 

 of Mr. Davidson's researches, I must refer the reader to his 

 valuable ' Monograph of Carboniferous Brachiopoda/ and to a 

 paper on "Scottish Carboniferous Brachiopoda" in the 'Geo- 

 logist/ But I would more particularly direct attention to 

 plate 54 of the Monograph, in which Carboniferous and Per- 

 mian individuals of each of the Brachiopods identified are figured 

 side by side, for the sake of comparison. The other species of 

 the list have been determined by Mr. T. Rupert Jones, Mr. R. 

 Howse, Prof. King, and myself. And it should not be forgotten 

 that this list is the result of a very partial investigation of Per- 

 mian and Carboniferous species. The Brachiopoda have cer- 

 tainly been pretty well examined, but this is the only class that 

 has. In other classes much remains to be done ; so it is possible 

 that future research may still further increase the number of 

 Carboniferous recurrent species, even in Britain. Had those 

 species which foreign authors consider to be common to Car- 

 boniferous and Permian strata been included, the list would 

 have received important additions. Dr. Geinitz, for example, 

 states that some of the plants of the Saxon Rothliegende are 

 identical with Coal-measure species*, as might, indeed, have 

 been suspected from the intimate relation that exists between 

 the flora of these rocks in Britain. M. Gceppert even asserts 

 that there are fourteen Permian plants referable to Carboniferous 

 speciesf. The interblending of Carboniferous and Permian 

 forms in North America would also seem to be considerable; 

 and American palaeontologists have already pointed out cases 

 of recurrency among the species of these formations. Accord- 

 ing to Dr. P. B. Shumard, Producta semireticulata, Martin, and 

 Spirifera camerata, Morton, so well known as Carboniferous 

 fossils, occur in the Permian rocks of the Gaudalupe Mountains 



* See Dr. Geinitz on the Coal Formation of Saxony, as noticed in Jour. 

 Geol. Soc. vol. xiii. p. cxxviii. 

 t Schlesische Gesellsch., Naturwiss. Sektion, 1858. 



