208 J. Marcou — Jura and Neocomian of Arkansas, 



General Classification of the Jura and N eocomian south of 

 the Arkansas river. — When, in 1887, Mr. Hill published his 

 first essay of a " Geologic Section of the Cretaceous strata of 

 the State of Texas, etc." (this Journal, vol. xxxiii, p. 299, 

 April 1887), I saw that there were important mistakes in his 

 classification of the Lower Cretaceous ; but I thought that he 

 would correct them, in his further researches. Instead of 

 improving his classification, however, and giving a clearer and 

 more exact nomenclature, confusion has been aggravated, until 

 I think it is time to interfere. 



It is strange, that almost perfect stranger as I am, for I have 

 explored a very small part of Texas, only a simple road in 

 the Panhandle — I should be obliged again to attempt a more 

 logical and exact classification, than the one in use by those 

 who have in charge the description of the geology of that 

 great and beautiful State. 



In 1860, Dr. B. F. Shumard published his " Section of the 

 Cretaceous strata in Texas " (Trans. Acad. Sc. of St. Louis, 

 vol. i, p. 582) ; and in 1861, I gave before the Boston Society 

 of Natural History a corrected section, reversing the whole 

 classification from top to bottom (Proceed. Boston Soc. Nat. 

 Hist., vol. viii, January 1861, p. 93). After many years of 

 opposition and discussion my classification has been accepted 

 as correct. It remained only to complete tlie details of sub- 

 divisions, and to keep the Jurassic formation distinct from the 

 Lower Cretaceous. Mr. Hill in bis first paper replaced the 

 Jura in tire Cretaceous, and ever since with some variations 

 has continued to identify the Jura either with the Washita 

 division, or with the lower part of what he calls the Lower 

 Cretaceous (Trinity division). Only once, after his first visit 

 to the Tucumcari region, has he recognized the strata contain- 

 ing the Gryphaza dilatata var. Tucumcarii and Ostrea Marshii 

 as Jurassic ; but as he said, he regretted it directly, and 

 returned with new vigor to his classification of the Texas Jura, 

 in the Lower Cretaceous. 



The constant changes in Mr. Hill's classifications render it 

 extremely difficult to understand the meaning of the names he 

 uses for the subdivisions, the great divisions and even his 

 name of " Comanche series," called first " Texas series."* It 

 is almost impossible to keep pace with him. Almost every 

 year since 1887, when he published his first classification, he 

 has brought forward a new one. To render the matter more 

 confusing, the Geological Survey of Texas has also used dif- 

 ferent classifications in its annual reports, and we have now 

 about ten different classifications to deal with. 



* Mr. Hill, in his nomenclature, uses the name ''Comanche Peak Group,'' 

 "Comanche Division'' and "Comanche series ;" rather too many Comanches. 



