'Weno and Pawpaw Formations 53 



Epiaster aguilerae Bose E. wenoensis Adkins 



Holaster simplex Shumard H. sp. 



Cyphosoma texana Roemer C. volanum Cragin 



Salenia mexicana Schlueter and S. texana 



Credner S " V lana Whlt " ey 



Goniopygus sp. G. budaensis Whitney 



Goniophorus sp. 1 G. sp. 2. 



COMPARISON OF PYRITE FAUNA 



TEXAS 



It has been pointed out' that the North Texas Comanchean system con- 

 tains a series of alternate lime and marl (or clay) formations, some of 

 which contain conspicuous pyrite and limonite faunae ; these are 



(1) The Kiamitia formation; 



(2) The Duck Creek marl; 



(3) The Denton marl; 



(4) The Pawpaw clay; 



(5) The Grayson formation; 



(6) The Del Rio clay. 



Many pyrite and limonite species are common to these six formations, 

 and still others have more restricted vertical ranges and are confined to 

 limited levels within a single formation. In general it may be said that 

 these fossils are of distinct species from those otherwise preserved in the 

 same formation ; that they are rare in the intervening formations, and that 

 the complexion of the limonite faunae is different from that of the other 

 faunal components of the formations in question. In addition there seem 

 to be certain limonite species in the various intervening limestone forma- 

 tions, especially in the Fort Worth and Weno limestones. To assist in de- 

 termining the age and correlation of these formations the following pro- 

 visional fossil lists are given. The list for the Pawpaw formation will 

 be found on page 51. 



The rather regular alternation of marl (or clay) and lime formations 

 in the North Texas section suggests some form of cyclic deposition, in 

 which the same marine conditions were many times repeated, and this 

 inference is equally strong for the contained pyrite faunae, when it is 

 found that they occur prevailingly in the alternate, clay, formations. This 



'Winton and Adkins: The Geology of Tarrant County, Univ. Texas Bull. 1931. 

 1920. 



