202 J. Marcou — Jura and Neocomian of Arkansas, 



" An interesting fact in the Black Hills and Blue Cut sec- 

 tions is that the large Gryphaea which comes in near the top 

 of the shales is identical with the form collected by Prof. 

 Marcou and is the species called Gryphcea Tucitmcarii by him 

 (later called Gryphcea dilaiata var. Tucumcarii)" 



" Prof. Marcou insisted that the beds from which this species 

 came were of Jurassic age, and upon its occurrence he main- 

 tained the existence of the Jurassic system in this region. It 

 occurs at Belvidere, as on the original plains of the Kiamitia 

 near Goodland, in Indian Territory, where it was last year col- 

 lected by Mr. T. Wayland Vaughan* of my division, and at 

 Kentf in Trans Pecos, Texas, stratigraphically above and inti- 

 mately associated with the species which he calls Gryphcea 

 Pitcheri. Thus we have in Kansas and Indian Territory Prof. 

 Marcou's alleged Jurassic species occurring stratigraphically 

 above species he called Cretaceous, which facts forever remove 

 any previous doubt, if any existed, in favor of his theory of 

 the existence of the Jurassic formation in Texas, Indian Ter- 

 ritory, New Mexican region." 



There is only a little difficulty in accepting the conclusion 

 drawn by Mr. Hill with such confidence, — the Gryphwa col- 

 lected in great numbers at the top of the section of Blue Cut 

 Mound, near Belvidere, is not the Gryphcea Tucumcarii ! 



1 have had in my possession, ever since 1888, beautiful and 

 perfect specimens of that Gryphoea, and the idea that a paleon- 

 tologist of the IT. S. Geological Survey and a chief geologist of 

 that Survey should call it G. Tucumcarii! was far from my 

 thoughts. When such discoveries were made, as those claimed 

 by Messrs. Hill, Stanton and Vaughan, their first duty was to 

 give good figures and exact descriptions of the Gryphcea and 

 put it side by side with the figures and descriptions given by 

 me in 1858 (Geology of North America, etc., plate IV and 

 pages 43 and 38, Zurich, 1858). But as it is a simple assertion,, 

 presenting no basis for discussion, the reader of Mr. Hill's 

 paper cannot judge from the paper itself. The Gryphcea 

 found on the top of the Belvidere section, above the beds con- 

 's* In Science, April 2, 1891, vol. v, No. 118, p. 559, Mr. T. W. Vaughan says 

 that he found in the vicinity of Arapaho (Oklahoma and Indian Territory) the 

 Gryphcea Tucumcarii of Marcou, a fossil asserted by him to be Jurassic, which 

 often occurs imbedded in the same matrix (as the Gryphcea Pitcheri of Marcou or 

 forniculata, of White). Thus he extends the error of Messrs. Hill and Stanton 

 farther south than Belvidere (Kansas). Figures and description of the so-called 

 G. Tucumcarii are entirely wanting, and Mr. Vaughan merely makes an assertion 

 without paleontological proofs — Note by J. M. 



f At Kent the Gryphcea Tucumcarii, which there is the true species, is not- 

 above the Gryphcea Pitcheri (G. Ecemeri) but below. And the pretended G. 

 Pitcheri of Messrs. Pumble and Cummins belongs to two new species entirely 

 distinct from the G. Ecemeri or Pitcheri (see " The Jura of Texas," loc. cit., p. 153). 

 —Note by J. M. 



