SOME UPPER CRETACEOUS SHELLS OF THE RUDISTID 

 GROUP FROM TAMAULIPAS, MEXICO. 



By L. W. Stefhenson, 

 Of the United States Geological Survey. 



OCCURRENCE. 



In March, 1920, the writer, while in the employ of the Mexican Gulf 

 Oil Co. (through the courtesy of whose officials this paper is now 

 published), discovered a few rudistids, representing several species, 

 associated with several other invertebrate species, in strata of Upper 

 Cretaceous age on two American-owned haciendas known, respec- 

 tively, as Chocoy and Las Flores (or Manuel), on the line of the 

 National Railways of Mexico between Tampico and Monterrey, in the 

 State of Tamaulipas, Mexico. Chocoy is owned by Mr. A. W. 

 Beckley, of Tampico, and Chocoy station is about 71 kilometers north- 

 west of Tampico. Las Flores is owned by Smith, Newell, and 

 Bishop, of Tampico, and Manuel station is 81 kilometers northwest 

 of Tampico. 



Subsequent to my first visit to these haciendas additional discov- 

 eries of rudistids and a few other invertebrates were made on Las 

 Flores hacienda by Mr. R. A. Bishop and on Chocoy hacienda by 

 Mr. Beckley and myself, as explained on subsequent pages. It is my 

 pleasure at this place to express my appreciation to the owners of 

 these properties for the courtesies which they extended to me on the 

 occasion of each of these visits. 



Two specimens of rudistids belonging to separate genera, found on 

 Chocoy hacienda in 1919 by Messrs. A. E. Fath and Eugene Steb- 

 inger, have been kindly placed at the writer's disposal, and one of the 

 specimens has been made the type of the new species Sauvagesia 

 color adens'is. 



The fossils were found in part in the uppermost beds of the San 

 Felipe formation, which is brought to the surface in this area by 

 broad anticlinal folds, and in part in the overlying Mendez forma- 

 tion. The San Felipe formation consists of 700 or 800 feet (200-250 

 meters) of regularly bedded platy limestone with subordinate inter- 

 bedded seams and thin layers of calcareous shale, there being, how- 

 No. 2422.-PROCEEDINGS U. S. NATIONAL MUSEUM VoL 61, ART. I. 

 20107— 22— Proc. N. M. vol. fil 1 1 



