ABT.l. EUDISTID SHELLS FROM MEXICO — STEPHENSON. 3 



about 10 kilometers west of Soledad and 3 kilometers east of the crest 

 of Tamaulipas range. The fossils were in a white, rather soft lime- 

 stone and included fragments of a large species of Inoceramus com- 

 parable with /. deformis Meek; to these fragments were attached 

 many small, irregular oysters which, though poorly preserved, have 

 the general appearance of Ostrea congesta Conrad. The exact 

 stratigraphic position of this fossil layer could not be determined, 

 but it is probably not less than 200 or 800 feet (60 to 90 meters) 

 below the top of the formation. 



The second locality was at the village of Santa Isabel, 21 or 22 

 kilometers east of Forlon station on the National Eailways of 

 Mexico; this station is 167 kilometers northwest of Tampico. 

 Numerous fragments of large Inoceramus shells with Ostrea conr- 

 gesta Conrad(?) attached and one poorly preserved rudistid were 

 observed in characteristic San Felipe rocks composing a fence, the 

 stones of which were obtained from outcrops of San Felipe lime- 

 stone in the immediate vicinity of Santa Isabel; the stratigraphic 

 position of these outcrops is thought to be about the middle of the 

 formation. 



The fossils found in the lower part of the Mendez shale include : 

 Foraminifers ; stems of crinoids of the genus Balanocrinus; echinoid 

 spines; fragments of Inoceramus; Ostrea plumosa Morton; repre- 

 sentatives of the family Eadiolitidae, including Sauvagesia hdti 

 Stephenson and unidentified fragments of Sauvagesla. 



The upper part of the Mendez yielded: Foraminifers; a few 

 crinoid stems of the genus B alanoorinus ; a few plates of an echinoid 

 test; representatives of the family Eadiolitidae, including Tampsia 

 hishopi Stephenson, T. chocoyensis Stephenson, and Sauvagesla 

 coloraden^'is Stephenson. 



On the basis of the large fragments of Inoceramus and of Ostrea 

 congesta Conrad ( ? ) , the San Felipe formation is correlated with the 

 Austin chalk of Texas and with the Niobrara chalk of the western 

 interior of the United States, 



Ostrea plumosa Morton, which occurs in both the upper part of 

 the San Felipe limestone and the lower part of the overlying Mendez 

 shale, has a stratigraphic range in the Atlantic and Gulf Coastal 

 Plain of the United States from the horizon of the upper part of the 

 Austin chalk to the top of the Cretaceous. 



Sauvagesla helti Stephenson, which is represented by one speci- 

 men from the lower part of the Mendez shale, is closely related to 

 and perhaps specifically identical with a species of Sauvagesla that 

 occurs in the Brownstown marl near White Cliffs, Arkansas. Since 

 the Brownstown marl corresponds in age to the lower part of the 

 type Taylor marl, S. helti affords a basis for regarding the Mendez 

 shale as approximately equivalent to the Taylor marl. 



