Vol. VIII, pp. 9-40, pls. I-VIII June 3, 1893 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON. 



Pi).LEONTOLOGY OF THP] CRETACEOUS FORMATIONS 

 OF TEXAS— THE INVERTEBRATE PALEONTOLOGY 

 OF THE TRINITY DIVISION/i^ 



BY R(3BERT T. TIILL.f 



CONTEx\TS. 



P.'ige . 



I. Strjitigraphic Divisions and Nomenclature of tlie romanche 



Series 9 



II. Position and Charactei'istics of tlie Trinity Division 12 



III. Fossils of the Trinity Division 15 



IV. Age and Significance of the Trinity I division 17 



V. Description of Species 20 



VI. Plates 40 



LSrRATIGRAPinC DIVISTONS AND NOMENCLATURE OF 

 THE COMANCHE SERIES. 



It lias heretofore been impossible to present iaunal stndies of 

 the paleontology of the various horizons of the Conianche Series, 



* Presented at a meeting of the Biological Society of Washington, Iield 

 January 28, 189.'>, and published by permission of the Director of the 

 United States Geological Survey. 



t The writer desires to express his indebtedness to the many friends 

 whose advice has assisted him in the preparation of this paper: to 

 Messrs. T. W. Stanton, AV. H. Dall, Alpheus Hyatt, and F. H. Knowlton, 

 of the United States Geological Survey, for aid in the determination of 

 doubtful genera, and to Mr. J. L. Ridgwaj', artist, and iVIr. C. "\V. F>ddy, 

 of Ware, Massachusetts, photo-engraver. 



2- BioT,. Soc. Wash., Vol. VIII, 1893. (9) 



