322 R. T. Hilt — Cretaceous Formations of Mexico. 



contain the typical Laramie fauna of Corbiculidie, Ostrea 

 wyomingensis, and Anomia micronemia. Still southward, 

 in another interior valley extending from Paderon — a vil- 

 lage east of Yenaditos — west to Jornos, the Montana- Laramie 

 beds form similar foot hills against the interior border of the 

 main mass of the Saltillo-Parras flank of the Eastern Sierra 

 Madre. 



On the east front of the Sierra Candella near Lampazos are 

 two vast mesas of this formation — Mesa Catahuana and Mesa 

 Patrias — the original Laramie localities where White first 

 studied this formation in Mexico. It occurs thence south- 

 eastward as far as Tampico. 



The participation of the strata of the Upper Cretaceous- 

 Laramie series in the mountain movements of the eastern Cor- 

 dilleras is further shown to the southward in the great Rincon- 

 ada passes of the eastern Sierra Madre between Monterey 

 and Saltillo where thousands of feet of the medial and lower 

 beds of the series are folded in the mountain structure. The 

 writer was not able to collect minutely from these beds bnt 

 found many of the characteristic Inocerami and Exogyra pon- 

 der osa of the Upper Cretaceous showing the participation of 

 the medial beds of the Upper Cretaceous in the movement as 

 well as that of the Laramie. 



While there is no doubt that there were some upland bodies 

 of water upon the western continent during the Upper Cre- 

 taceous and Laramie epoch, especially during the emergence of 

 the land in the latter part of the epoch, it can hardly be said 

 that these sediments are fresh water deposits in the sense that 

 they were not laid down at marine base level, for there is every 

 evidence that the larger part of the Laramie and Upper Cre- 

 taceous deposits along the whole front of the eastern Cordil- 

 leran region both in the United States and in Mexico were 

 laid down at marine base level adjacent to the great western 

 continent that existed over the nucleal Cordilleran region at 

 that time, and that the idea of one great enclosed Laramie in- 

 land sea must be abandoned. * 



This Upper Cretaceous Eocene (Laramie) deposit undoubt- 

 edly represents the last littoral of the Atlantic along the 

 eastern front of the older Cordilleran region prior to the last 

 great folding, for none of the Claiborne Eocene fossils such as 

 occur in the same series of sedimentation above the Laramie 



* It is impossible here to discuss the Laramie question at length. Stanton and 

 Cross in this Journal have both recently shown that several distinct formations 

 have been confused under this name. In this paper the word is used to describe 

 those sedimentations that insensibly succeed the last known beds containing 

 unmistakable Cretaceous fossils and which like them were laid down at marine 

 base level and containing estuarine, marine and fresh water fossils described by 

 White and Meek under the name Laramie. 



