4-1 PROCEEDINGS OF WASHINGTON MEETING. 



occurs. This is true. It deprives Scolithus, too, of any value as a means of correlat- 

 ing rocks of two different sections, one with another. This is also true, and so it 

 should be. Xo valid argument can be brought forward to justify placing the rocks 

 of two widely separated areas in the same terrane upon the evidence of such a form 

 as Scolithus — a form of indefinite character, of indefinable features, of perplexing 

 variability, and of wide time range. The use of forms of this sort as a means of 

 correlation is even worse than the use of lithological character. Time does not 

 permit mentioning the erroneous correlations resulting from the use of Scolithus, but 

 they are numerous enough. 



A second objection urged will probably be the multiplication of names resulting. 

 Some will, perhaps, prefer to let Scolithus linearis do duty for all the forms if they 

 can be shown to be indistinguishable ; but this objection does not seem to me to be 

 a valid one. Dr. C A. White, in a paper read before the American Association for 

 the Advancement of Science last year and published in volume 39 of the proceed- 

 ings, in speaking of applying new names to fossils occurring in two different forma- 

 tions, says that " if a given formation is found to bear a fossil fauna the component 

 members of which, witli such exceptions as have been referred to (i. e., forms con- 

 sidered identical in two formations) are all unlike those of any other known fauna, 

 I think it admissible to treat the whole fauna as new and to give a new name to 

 each species" (p. 242). My own studies of Scolithus led me to adopt this method 

 previous to reading Dr. White's paper, and I have therefore proposed, as seen above, 

 to characterize the species of Scolithus upon the formation, and not, as has been 

 done at times, the formation on the occurrence of the species. 



The paper by Mr. James was discussed by N. S. Shaler and E. W. 

 Claypole. Professor Shaler advised neglecting altogether the specific 

 names for Scolithus, since it is at best only a hole in the rock. He also 

 regarded Billings' observations on sponge spicules as valueless, because 

 anything so widely distributed as these spicules would be readily swept 

 into small crevices or openings, such as the Scolithus perforations. Pro- 

 fessor Claypole remarked that Scolithus persists to the present time. 



The following paper was then read : 



* 



THE TERTIARY IRON ORES OF ARKANSAS AND TEXAS. 

 BY R. A. F. PENROSE, JR. 



Contents. 



Distribution of the Ores Page 44 



Geologic Relations of the Ores 45 



Nature of the Ores 46 



Nodular Ores 46 



Laminated Ores 46 



Origin of the Ores 47 



Conclusions 50 



Distribution of the Ores. 



The Tertiary iron ores of Arkansas and Texas as now found are hydrous sesqui- 

 oxides of iron, generally occurring as limonites or allied forms. They occupy a belt 

 of country running northeastward and soutbwestward through the southern part 



