472 JR. T. Hill — Uppermost Cretaceous Beds of the 



Arkansas glauconite beds above the Ponderosa marls and lower 

 divisions of the Upper Cretaceous in Texas. The fauna of 

 these uppermost glauconitic beds of Arkansas and Texas, 

 described in my Arkansas report* is the characteristic fauna of 

 the Mississippi beds, and not of the underlying Ponderosa 

 marls, except a few connecting species 



Continuing our investigations northward into the New 

 Jersey region we find there the greatest development of these 

 glauconitic beds and a continuation of the Arkansas fauna. 

 Closer scrutiny shows that this correlation can be extended 

 only to the lower marl beds of New Jersey for the Arkansas 

 representative, or continuation of the middle marl beds has 

 been eroded and destroyed during the post Cretaceous land 

 epoch {Laramie time) and the Tertiary overlap. The paleonto- 

 logic proof of this is indisputable, the molluscan faunas being 

 almost identical. Among the lammelibranchite species com- 

 mon in America to Arkansas, Texas, Mississippi and the lower 

 marl beds of New Jersey are the following : 



Ostrea larva, Lamck. 



JEhogyra costata (typical var.), Say. 



Gryphcea vesicular is Lamck. and vareities, such as G. vomer, G. 

 convexa and G. pyenodonta. 



Comptouectes simplicum Con. 



JSTeithea quinquecostataf 



Idonearca tippana Con. 



Trigonia eufalensis Gabb. 



Inoceramus barafini Mort. 



Pachycardium spillmani Con. 



Aitomia argentu, and numerous other species. 



None of these forms, according to Whitfield, except G. 

 vesicularis, occur in New Jersey in other than the lower marl 

 bed, while in Arkansas, Mississippi and Alabama they charac- 

 terize the glauconitic division, and in Texas are barely repre- 

 sented by two species in the uppermost Ponderosa marl beds, 

 but occurring in the island of Anderson county as in Arkansas. 



Furthermore, none of the characteristic fossils of the New 

 Jersey Cretaceous above the lower marl bed, such as Terebratida 

 harlani, the JBelemnitella mucronata, and the Ammonites 

 placenticeras occur in the Arkansas-Texas Cretaceous, — only 

 two specimens of JB. mxicronata having been found in that 

 region, and there in the contact debris at the base of the 

 Tertiary where they were preserved from destruction by their 

 hard, siliceous composition. 



In the light of the above paleontologic and lithologic facts, 

 the only logical conclusion is that the uppermost beds of 

 Arkansas are the southwestern representative, perhaps the 



* Not having had the opportunity of reading the proof of that report, the au- 

 thor begs to be excused for the tj r pographic errors in the list of fossils. 



