FORT WORTH LIMESTONE AND FAUNA. 327 



ness and in proportion to the marls in ascending series, the latter passing 

 without break into the ferruginous Denison beds. 



While these beds resemble the Duck creek limestones in color and 

 composition, the material of the latter is certainl}^ clearly distinguishable 

 by its purer, finer grained and more chalky character. If there is any 

 doubt upon this point, however, its paleontologic differentiation is un- 

 mistakable. 



Paleontologically the Fort Worth limestones may be defined in the 

 Denison section as including the beds between the hemeras of the un- 

 described Inoceramus, sp. noA^, above mentioned and Ostrea qaadrwplicata, 

 Shumard. 



The paleontologic character of the Fort Worth beds is very persistent 

 throughout their extent, but their lithologic aspect is sometimes repeated 

 in some of the horizons of the Denison beds in their southward extension, 

 as they become more marly away from the Ouachita shore at Denison. 

 In the Denison section the beds are about 200 feet thick, and the follow- 

 ing fossils, the list of which is subject to future revision, have been re- 

 ported from them : 



Fauna of the Fort WortJt Limestone.'^ 



Fschara sp. Vola hellnla, Cragin. 



Epiaster elegam, Shumard. Nelthea catherlna, Cragin. 



Hohclypiis planatua, Roerner. " occidentalis, Conrad. 



Letocidaris hem'igranosits, Shumard. Janira vrighiii, Shumard. 



Cldaris texanaa, Clark. Lima gcnerom, Cragin. 



Pyrina parryi, Conrad. " ivacoensis, Roemer. 



Ostrea carlnata, Lamarck. Turritella serlathu grannlafa, Roemer. 



" diluviana, Lamarck. " piandateras, Conrad. 



Gryphiea pitcheri, Morton. Pleurotomaria austinensis, Shumard. 



" sinuata, \^. americana,MiiYcou. Nautilus texanns, Shumard. 



Plicatula placnnea (?), D'Orbigny. Amiiiomtesleoru'n.n'is, Conrad. 

 Spondylus lillli, Cra«;in. 



Denison Beds. — Succeeding the Fort Worth limestone in the North 

 Texas section is a grouj) of lithologic and paleontologic members, for which 

 I proposed the collective name of the Denison beds in previous papers,t 

 and deferred a minute definition of its members until a future occasion. 



•The term Fort Worth limestone is applied to several distinct beds by Mr Taflf, who appears to 

 have used the term sometimes to describe lithologic appearance as well as position. See section, 

 pp.269, 270, of his report in Fourth Annual of the Texas Survey, where he has it twice, with " Den- 

 ison marls" between. He also includes in it (p. 2G) the Denison fauna. 



fSee Preliminary Annotated Check-list of the Invertebrate Cretaceous Fossils, Austin, 1884, p. 

 xxiv; Bull. Geo!. Soc. of Am., vol. 2, May, 1801, p. 517 ; On the Occurrence of Artesian and other 

 Underground Waters in Texas, etc, Washington, 1892, p. 88. 



