314 i?. T. Hill — Cretaceous Formations of Mexico. 



of the associated faunas. This genus is characteristic of the 

 Upper Cretaceous of the world, but unfortunately there are 

 no true Hippurites in the Lower Cretaceous of the United 

 States while their occurrence in Mexico is not proven. All 

 the species so-called belong to the lower ranging genera 

 Sphserulites and Radiolites which in Europe especially in 

 Portugal* have the identical position they have in the Texas- 

 Mexican region, i. e. they occur in a narrow zone between 

 the true Monopleura and Caprina beds of the Neocomian and 

 the Gault just as it ranges in Texas between the Monopleura 

 and Caprina beds of the Glen Rose (Neocomian) and the 

 Washita (Gault) division. Dr. Roemer distinctly states in his 

 description of " Hippurites " texanus that he is in doubt 

 whether to refer it to the genus Hippurites or Radiolites, and 

 from careful studies of abundant material in my collection it 

 can be seen that the genus is clearly not Hippurites, but has 

 strong resemblance to the Sphaerulites of Portugal. 



Felix and Lenk in their careful presentation of the Tehuacan 

 or Monopleura beds (Glen Rose beds of my Texas section) 

 show beyond doubt their Neocomian equivalency, and refrain 

 from correlation of the "Hippurites" limestone with the beds 

 of northern Europe. f 



If those who doubt the Neocomian position of the faunas 

 of basal half of the Comanche Series will compare my un- 

 published collections in the possession of the Texas Geo- 

 logical Survey and at my residence in Washington with the 

 beautiful Cretaceous faunas of Portugal as illustrated by 



* The so-called " Hippurites " of the Texan (Comanche) Cretaceous are entirely 

 different in specific characters from the well known Hippurites of the Upper 

 Cretaceous of Europe, but are of the genera Sphaerulites and Radiolites of 

 Lamarck which in Europe begin in the Lower Cretaceous. It is unfortunate that 

 no systematic study of the biological relations of the American forms has been 

 attempted None of the aberrant molluscan forms like Monopleura, Requienia, 

 Plagioptychus, Caprina, Rudistes, and the alleged Hippurites range higher in the 

 Texan Cretaceous than the Caprina limestone of the Comanche Series and only the 

 entirely distinct generic form called Radiolites Austinensis type (Roemer) has been 

 found in the Upper Cretaceous, while no Hippurites especially of the European 

 type of H. cornu-vaccinum have not been found in America. 



f Dr. Roemer, who committed the same error of placing the " Hippurite " bear- 

 ing Lower Cretaceous of Texas in the Upper Cretaceous of Europe as others who 

 have visited Mexico are now doing with the Hippurites limestone of that country, 

 also wrongly concluded that the Monopleura fauna sent him from near Austin was 

 from the Upper Cretaceous limestone instead of from the Caprina limestone and 

 Glen Rose beds. See " Ueber eine durch die Haufigkeit Hippuriten Artigen 

 Chamiden ausgezeicb.net Fauna der Ober Turonienkreide von Texas. Paleon- 

 tologischen Abhandlungen. IV Band. Heft 4. Berlin, 1887. Reviewed in this 

 Journal by the writer in vol. xxxvii, 1889, pp. 318-319. Although admitting that 

 it was different from anything he had known in Europe under the impression that 

 it came from the Austin chalk, which has Turonian fades, he entitles it a Turonian 

 fauna and so describes it. In all European paleontological treatises, notably Zittel 

 and Steinman, these are shown to be characteristic genera of the Neocomian. 



