Vol. VIII] DUMBLE— GEOLOGY TAMPICO EMBAYMENT AREA 153 



division of the Middle Cretaceous, one of these being to the 

 south of Apasapan, and another near Santa Maria Tatetla, 

 where there are Hmestone beds carrying Riidistcs, Actcsondla, 

 Nerinca, etc. At Palmer the limestones carry Caprina and 

 other Cretaceous fossils. On top of these come calcareous con- 

 glomerates, marls, and sands somewhat consolidated and sand- 

 stones carrying the fauna described as Pliocene. Above the 

 fossiliferous beds come a conglomerate of modern eruptive 

 rocks. 



The Tertiary fossiliferous bed occurs at an altitude of 280 

 meters above the sea-level, and, in the bottom of the barranca, 

 about four kilometers below Santa Maria. The bed extends 

 eastward and the same fossils are found in a somewhat harder 

 limestone at an elevation of 150 meters at Puente Nacional. 

 That the beds dip to the east may be seen from the altitude of 

 the fossil localities. 



The sandstones and sand in the Barranca Santa Maria admit 

 of two divisions : Ostrca, Ammussium and Encopc are the more 

 abundant in the lower division and in the upper there are 

 numerous bivalves of other genera and gasteropods, but, with 

 the exception of Ammussium, the species are rather scarce. 

 Both divisions carry many forms in common and are un- 

 doubtedly of the same age. 



The fauna found in this region comprises the following : 



Encope Tatedaensis, n. sp. (frequent) 

 Pecten Aztecus, n. sp. 



" santarosanus Bose 

 Ammussium mortoni Rav. (frequent) 

 Pinna serrata Sow. (frequent) 

 Anomia simplex D'Orb. 

 Ostrea virginica Gmelin (frequent) 



" sculpturata Conr. 

 Area taeniata Dall. 

 Lucina quadrisulcata D'Orb. 



" pectinata Gmelin 

 Laevicardium sublineatum Conr. (frequent) 

 " serratum Linnaeus (frequent) 



Dosinia elegans Conr. (frecjuent) 



" acetabulum Conr. (frequent) 

 Venus ebergenyii Bose (frequent) 



