R. T. Hill — Texas Section of American Cretaceous. 307 



A review of the fossils of the Comanche series shows that 

 the Amrnonitidse, which are especially abundant in the Washita 

 Division, consist of the sharp-keeled and flexuous-ribbed forms 

 so characteristic of the Lower Cretaceous, while the genus Crio- 

 ceras (Ancyloceras) is represented by several species absolutely 

 indistinguishable from Neocomian forms. The characteristic 

 Ammonites pedernalis Von Buch (not Binkhorst), of the Co- 

 manche Division, is an aberrant archaic ceratitic form. The 

 only brachiopod of the Comanche series, which occurs about 

 midway in the Washita Division, the Terebratula wacoensis 

 Eoemer, was confessed by its author to be very near T. semi- 

 globosa Sow., of the Neocomian. The Echinodermata all belong 

 to genera which had their origin in or previous to the Lower 

 Cretaceous, and have great affinities to the European forms, 

 one of which is almost indistinguishable from the characteristic 

 Toxaster complanalus. The Ostreidas mostly belong to the deep- 

 water, and now extinct sub-genera Gryphsea, Exogyra, and 

 Alectryonia, a great number of which present none of the con- 

 fusing variation of the later Ostreidse. The anomalous Gryphcea 

 Pitcheri, which is an exception to the last generalization, instead 

 of having been originally described from New Jersey and be- 

 ing the most widely distributed form of the Cretaceous in 

 the United States, as has been asserted, was originally 

 described from Indian Territory, and is almost if not entirely 

 limited to the Comanche Series, except a few forms from the 

 overlying shales of the Rocky Mountain region. This is a 

 Jurassic form, which has continued up into the Cretaceous of 

 this country, and the naviate variety is almost indistinguishable 

 from the 0. arcuata of the European Lias. It was chiefly upon 

 the evidence of the Exogyra texana and the Os/rea carinata that 

 Eoemer made this Comanche series belong to the Upper Chalk 

 of Europe, but according to modern biologic methods these 

 forms really belong to two well-marked ostreidean types that 

 have been described under a host of names, which have the 

 widest vertical range of any Cretaceous forms, and the Texas 

 individuals bear much greater resemblance to the basal varie- 

 ties of the Neocomian than to those of the Chalk. The Capro- 

 tina of Eoemer is the genus Requienia, characteristic of the 

 European Lower Neocomian, and the widely distributed single 

 species characteristic of the Fredericksburg Division of the 

 Comanche series, which has been described under many syno- 

 nyms, is hardly distinguishable from the characteristic Capro- 

 Una Lonsdalii D ; Orb., of the European Neocomian. TheEudis- 

 tes, Nerineas, Pleurotomarias, Globioconchas, and other forms, 

 while not decisive, are corroborative of the low position of the 

 Comanche series. This opinion is strengthened, furthermore, 

 by the occurrence of many other forms, and the absence of any 

 species characteristic of the upmost Cretaceous. 



