324 



R. T. HILL GEOLOGY OF RED RIVER. 



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The fossils occur throughout in definite zones and 

 associations. The thicker Fort Worth beds at the 

 base may be paleontologically characterized as the 

 zone of the unique Epiastei- elegnns of Shumard 

 (Macraster texanus of Roemer) * and the Ammonites 

 {Schloenbachia) leonensis, Conrad. 



Above these is a bed of chxy, ahnost an ag- 

 glomerate, of Gnjphsea pltcherl of Morton, not 

 others.t Associated with this is the unique oyster 

 Alectryonia carinata, a familiar European form, 

 occurring only at this horizon in the American 

 section. 



At the top of the column is the massive Kingena 

 limestone, which is set with Kingenas like raisins 

 in a pudding. Paleontologically, the term Fort 

 Worth limestone should be hereafter limited to the 

 lowest member of this Austin section or to the 

 thicker beds carrying Epiaster elegans and Schloen- 

 bachia leonensis, for the few feet of upper marls are 

 probably the southern attenuation of the lowest 

 Denison or Marietta beds. The lower (Preston) 

 subdivision of the W^ashita has not been found at 

 Austin. Let us now compare the Austin section 

 with that of Denison. 



Denison Section. — At Red river the Washita di- 

 vision is much more fully developed, presenting 

 several distinct subdivisions which do not occur 

 at Austin, the whole section thereby being greatly 

 thickened. 



Kiamitia Clays.J — The firm, chalky, crystalline 

 Goodland limestones, the northern representative of 

 the Fredericksburg division, are succeeded by about 

 fifty feet of dark colored, marly, laminated cla3^s, 

 which are often nearly black before oxidation. They 

 alternate with thin flags of dark blue limestone, 

 oxidizing dirty yellow, and are composed almost 

 entirely of the shells of Gryphsea fornicidata oi 



*Neues Jahrbuch fiir Geologie, Jahrgang, 1888. 



■f G. washita, of my making. This is the only form of the five dis- 

 tinct species of Gryphcea which have been almost inextricably con- 

 fused under the name of G. pitcheri, which is Morton's original 

 species. The whole subject is being treated by the writer in a 

 separate paper. 



X First defined in Bull. Geol. Soc. Am., vol. 2, p. 515. 



