Jura, Neocomian and Ghalk of Arkansas. — Marcoa. 3(i5 
Jurassic (Tueumcari beds) — Gryphxa dilatata var. Tucumcarii 
Marc, and Ostrea marshii Sow. and Marcou. 
Under the title Gri/phma pitcher I Morton, professor Hill 
gives, at pp. 168-173, a long and quite correct account of the 
confusions and controversies created by my adversaries. I 
shall only point out two errors. Professor Hill thinks that 
"this species has such a striking Jurassic aspect ; " it is a very 
incorrect view, Avhich he would not have taken if he had had 
a practical knowledge of the Jurassic and Cretaceous Euro- 
pean systems ; for at first sight, with my long experience of 
Jurassic and Cretaceous in the Jura mountains, I recognized 
the Neocomian form of Oryphwa^&o characteristic in Gryphaia 
Gouloni of Neuchatel ; and I had no hesitation to say in 1853 
when in the field at Comet creek, on the bank of the Washita 
river, that I had before me the equivalent and the homotaxis 
of the Neocomian great formation of Europe. 
All that professor Hill says about my figures 1, called by 
error (3), and 2, called by error fig. (1), of the Gryphoea 
dilatata old and young, is incorrect ; my figure 2 is not a 
"small and imperfect figure," but on the contrary an excellent 
drawing of a 3^oung individual of G. dilatata var. tucumcarii, 
which has nothing to do either with the G.pitcheri Morton or 
the G- pitcheri variety dilate of Hill. 
For the first time, thirty-five years after I niade my explor- 
ation in the Indian territory, Texas and New Mexico, a practic- 
al geologist, who knows stratigraphy, has seen the Tueumcari 
area. Professor Hill, after a fcAv hours' stay at Little Tueum- 
cari, returned convinced that the Gryphwa tucumcarii is not 
the Gryphoia pitcheri, and that the "unquestionable Creta- 
ceous" beds of Messrs. James Hall, the Shumards and J. S. 
Newberry belong to the Jurassic system. 
Professor Hill has an interesting chapter xiv, on the pres- 
ence of "Chalk in the North American Cretaceous." He says 
that "although certain Cretaceous beds * * * of the Nebras- 
ka formation of the upper Missouri, have ])een exceptionally 
alluded to as of a chalky nature * * * f "the term chalk 
has been studiously avoided in lithologic description" by 
American writers, because they have "the idea ihni'true chalk 
does not occur in the United States." This is rather too 
exclusive and incorrect. Evidently my discovery of the true 
chalk near Sioux City (Iowa) and in Nebraska in 1803, has 
