36 University of Texas Bulletin 



The small number of ammonoids found in the lowest part of the 

 zone of Prothalassoccras and the imperfect knowledge we have 

 about those Russian forms which appear to be their nearest 

 relatives, impedes us in drawing accurate conclusions with re- 

 spect to the age of our horizon. Nevertheless, the circumstance that 

 upon that zone rests one whose fauna has intimate relations with that 

 of the Sosio beds, and which for its part is covered by another zone 

 the fauna of which without doubt is synchronous with that of the Sosio 

 beds, makes it very probable that our Hess limestone is a representa- 

 tive of the cephalopod-bearing sandstone of the Artinsk. This opinion 

 is confirmed to a certain degree by the fauna of the zone which is 

 found below the Hess limestone. 



The ammonoids contained in the Wolfcamp formation or zone of 

 Uddenites have an entirely archaic character and are different from 

 any fauna so far described. The following table shows these features 

 more clearly and will serve as a base for further discussion. 



SPECIES FROM THE WOLFCAMP FORMA- COEEESPONDING FOEMS AT OTHEE 



TION, GLASS MOUNTAINS 1 LOOALITIES 



DaraeUtes texanus n. sp. D. elegans Tchernow, Artinsk, Russia 



Uddenites Scliucherti n. sp. : 



Uddenites minor n. sp. 



Gastrioceras modestum n. sp. G. subcavum M. a. G., Cisco forma- 



tion, Texas. 



ScJiistoceras diver secostatum n. sp. 8ch. Hyatti Smith, Cisco formation, 



Texas. 



Paralegoceras incertum n. sp. 



AgatJiiceras Frechi n. sp. A. walicmn Karp., Artinsk, and 



Upper Carb., Russia. 



Marathonites J. P. Smithi n. sp. ? Stacheoceras Bomanowskyi Karp., 



Artinsk, Russia. 



Marathonites sulcatus n. sp. ? StacJieoceras Ganti Smith, Cisco 



formation, Texas. 



Marathonites vidriensis n. sp. ? Stacheoceras Ganti Smith, Cisco 



formation, Texas. 

 Vidriaceras Uddeni n. sp. - 



Yidrioceras irregulare n. sp. 



We recognize at once how little similarity there is between our 

 fauna and any other. Forms like Uddenites, Paralegoceras incertum, 

 and Vidriaceras are types unknown from any other locality, and it is 



