Age of the Trlidttj Division. 19 



comian, V. lujaiil De Verneuil and which in every variation is 

 identical with the figures of the European species. 



Natlca (^Tiflostoma) pedcrnalis Roemer is characteristic of the 

 Tylostonias of the Neo(3omian of France, Spain, and PortugaL 



Of the Nerinxas in the Texas beds all have the archaic form 

 of the Jurassic and lower Cretaceous (Neocomian) Nerina^as. 



Only one echinoid is found in the Trinity Division, Epiaster (?), 

 l)utthis is of the older Cretaceous aspect of the European forms. 



Of the Ainmo)iitl(Ue, which in Europe are most relied upon for 

 the classification of subdivisions of the Cretaceous, it may be 

 said that the Comanche Series below the Washita Division 

 is very deficient in these, only four species being known in 

 America. Of two of these only three individual specimens 

 have been found, while the European Neocomian abounds in 

 many si)ecies and genera. Of the two genera with one species 

 each found in the Trinity Division, it may be said that one of 

 them, Neumayrla, belongs to a genus which occurs in the Pur- 

 Ijcckian, or uppermost Jurassic, and Wealden of Europe, and 

 hence may be accepted as strong evidence that these beds are 

 not of late Cretaceous age. Tlie other species, Acanthoceras (?) 

 jastinas, is too poorly preserved to be of criterional value. 



While the writer has throughout placed the Trinity Division 

 in the Cretaceous, he tried to defer final discussion of their age 

 until opportunity should arrive for careful study of these fossils. 

 Owing to constant labors in the field upon the more important 

 stratigrajihic problems, this opportunity did not arrive until 

 now. At the time the Arkansas report* was written it was held 

 that the Trinity beds miglit prove to be Jurassic, but the careful 

 revision here presented tends to remove this doubt and enables 

 us to assert their Cretaceous age witli more assurance. Wliat- 

 ever doul)t may have been inferred frt)m any expressions in 

 l^revious ]ju]jlications,t it may now be stated positively : 



* Op. cit. 



t Throii<^li two unfortunate lapses in the typography of his foruun- 

 papers the attempt has been made to show that the writer did not hold 

 the Cretaceous age of the Trinity Division, notwitlistanding his repeated 

 pubUcations to the contrary. One of these is caused by the typographic 

 error on page Si of the report " On the Occurrence of Underground 

 Waters," etc., AVashington, May, 1892, where the clause •' which are as- 

 sumed to be the base of the true Cretaceous " is made to modify the words 

 " Walnut clays," instead of " these beds," i. e., the Trinity. The other 

 lapse was of a somewhat similar nature in the previous publication on The 

 Comanche Series of the Texas-Arkansas Region. 



