64 University of Texas Bulletin 



question. These sharks also occur in the intervening limestone forma- 

 tions but their abundance in the marls and clays testifies to the favorable 

 conditions for their existence. 



In view of the importance which these pyrite faunae may have for 

 correlation purposes, it is considered useful to refer to certain pyrite 

 faunae of approximately the same age known from Europe and Africa. 

 Of these the Vraconian fauna investigated by Pervinquiere shows the 

 closest similarities to the Pawpaw fauna here described, notably in the 

 ammonites. The bearings of these fossils on the correlation of the Paw- 

 paw formation have been discussed elsewhere (page 42). It is evident 

 that unless conditions for the pyritization of fossils are worldwide at 

 a given time, it is useless to attempt to make exact correlations of Texas 

 pyrite zones with particular zones abroad. Instead, those pyrite fossils 

 which have limited vertical ranges may, like any other such fossil, be 

 used to mark within narrow limits the age of the zone in which the fossil 

 occurs. A list of similar Texas and foreign pyrite and limonite species 

 is added. 



EUROPE AND AFRICA 



European Limonite and Pyrite Faunae 1 



VALANGIAN 



Sayn 2 has described a series of pyritic ammonites from the Valangian of Provence 

 and Dauphine; this fauna consists prevailingly of species of Lytoceras, Phylloceras, 

 Garnieria, Neocomites, Thurmannia, Mortoniceras and Leopoldia. 



ALBIAN 



In the Haute-Marne, near Montierender are two gray sand layers with pyritic 

 ammonites, separated by one meter of clayey sand. 



Upper Level: 



Lower Level: 



Hoplites deluci 



denarius Desmoceras beudanti 



splendens Hoplites deluci 



auritus denarius 



Turrilites catenatus quercifolius 



Hamites rotundus Douvilleiceras mamillatum 



lyelli 



Inoceramus concentricus Hamites alternotuberculatw 



Nucula pectinata Belemnopsis minimus 



iHaug: Traite de Geologic, pp. 1232-1298. 



2 G. Sayn, Les ammonites pyriteuses du sud-est de France. Mem. Soc, Geol. France. 

 No. 23, 1901. 



