114 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Texas, and who had had a year's experience in connection with 

 artesian water investigations in northeastern Mexico, was 

 placed in charge of the work, which began with an effort to 

 connect the known geological section of the Texas side of the 

 Rio Grande with the formations of the Mexican oil fields. The 

 results of this work, as given in a paper entitled "Tertiary 

 Deposits of Northeastern Mexico"^ show that the Gulf Coast 

 Tertiary deposits which carry the Texas oil are not represented 

 in the Tampico-Tuxpam oil fields, but that the oil formations 

 there are a continuation of the Cretaceous." 



During the years which have followed, the geologists of the 

 Southern Pacific Company have continued work in this area 

 under the direction of the writer and much information has 

 been accumulated regarding the stratigraphy and some good 

 collections of fossils have been made, the most of which were 

 placed in the hands of Dr. R. E. Dickerson, Curator. Depart- 

 ment of Invertebrate Paleontology, California Academy of 

 Sciences, for identification. 



It is proposed in this paper to give briefly the results of our 

 work and, based on Dr. Dickerson's and Dr. W. S. W. Kew's 

 determinations of the fossils, to show as nearly as possible the 

 ages of the formations encountered. Descriptions of the col- 

 lections have been made by Dickerson and Kew in a separate 

 paper^. 



The Area 



The region under consideration is a narrow belt of country 

 on the eastern coast of Mexico, beginning just north of the 

 twentieth parallel and extending to the twenty-fourth. From 

 Nautla to Tampico it comprises the entire coastal strip lying 

 between the Cordilleras, or Sierra Madre Oriental, and the 

 waters of the Gulf of Mexico. North of Tampico it is bounded 

 on the west by the Cordilleras and on the east by the Tamauli- 

 pas range, thus forming the valley through which runs the 

 railway between Tampico and Monterey. 



This area is the northern portion of what has been called the 

 Tampico Embayment.* It is economically important because 



' Proc. Cal. Acad. Sci., 4th Series, Vol. V, No. 6. 



' Dumble, "The Occurrences of Petroleum in Eastern Mexico as Contrasted with 

 those in Texas and Louisiana." Trans. A. I. M. E. August, 1915. 



•A Medial Tertiary Fauna from Northeastern Mexico. Proc. Cal. Acad. Sci. 1917, 

 Vol. VII. No. 5. 



* Some Events in the Eogene History of the Present Coastal Plain of the Gulf of 

 Mexico in Texas and Mexico. Journal of Geology, Vol. XXIII, No. 6, p. 481 et seq. 



